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The Ethereal FAQ Note: This is just an ASCII snapshot of the faq and may not be up to date. Please go to http://www.ethereal.com/faq for the up to date version. The version of this snapshot can be found at the end of this document. INDEX General Questions: 1.1 Where can I get help? 1.2 What protocols are currently supported? 1.3 Are there any plans to support {your favorite protocol}? 1.4 Can Ethereal read capture files from {your favorite network analyzer}? 1.5 What devices can Ethereal use to capture packets? 1.6 How do you pronounce Ethereal? Where did the name come from? Downloading Ethereal: 2.1 I downloaded the Win32 installer, but when I try to run it, I get an error. 2.2 When I try to download the WinPcap driver and library, I can't get to the WinPcap Web site. Installing Ethereal: 3.1 I installed an Ethereal RPM, but Ethereal doesn't seem to be installed; only Tethereal is installed. Building Ethereal: 4.1 The configure script can't find pcap.h or bpf.h, but I have libpcap installed. 4.2 Why do I get the error dftest_DEPENDENCIES was already defined in condition TRUE, which implies condition HAVE_PLUGINS_TRUE when I try to build Ethereal from CVS or a CVS snapshot? 4.3 The link fails with a number of "Output line too long." messages followed by linker errors. 4.4 The link fails on Solaris because plugin_list is undefined. 4.5 The build fails on Windows because of conflicts between winsock.h and winsock2.h. Using Ethereal: 5.1 When I use Ethereal to capture packets, I see only packets to and from my machine, or I'm not seeing all the traffic I'm expecting to see from or to the machine I'm trying to monitor. 5.2 I can't see any TCP packets other than packets to and from my machine, even though another sniffer on the network sees those packets. 5.3 I'm only seeing ARP packets when I try to capture traffic. 5.4 How do I put an interface into promiscuous mode? 5.5 I can set a display filter just fine, but capture filters don't work. 5.6 I'm entering valid capture filters, but I still get "parse error" errors. 5.7 I saved a filter and tried to use its name to filter the display, but I got an "Unexpected end of filter string" error. 5.8 Why am I seeing lots of packets with incorrect TCP checksums? 5.9 I've just installed Ethereal, and the traffic on my local LAN is boring. 5.10 When I run Ethereal on Solaris 8, it dies with a Bus Error when I start it. 5.11 When I try to run Ethereal, it complains about sprint_realloc_objid being undefined. 5.12 I'm running Ethereal on Linux; why do my time stamps have only 100ms resolution, rather than 1us resolution? 5.13 I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why are the time stamps on packets wrong? 5.14 When I try to run Ethereal on Windows, it fails to run because it can't find packet.dll. 5.15 I'm running Ethereal on Windows; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? 5.16 I'm running on a UNIX-flavored OS; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? 5.17 I'm running Ethereal on Windows NT/2000/XP/Server; my machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the "Interface" item in the "Capture Options" dialog box. Why can no packets be sent on or received from that network while I'm trying to capture traffic on that interface? 5.18 I'm running Ethereal on Windows 95/98/Me, on a machine with more than one network adapter of the same type; Ethereal shows all of those adapters with the same name, but I can't use any of those adapters other than the first one. 5.19 I'm running Ethereal on Windows, and I'm not seeing any traffic being sent by the machine running Ethereal. 5.20 I'm trying to capture traffic but I'm not seeing any. 5.21 I have an XXX network card on my machine; if I try to capture on it, my machine crashes or resets itself. 5.22 My machine crashes or resets itself when I select "Start" from the "Capture" menu or select "Preferences" from the "Edit" menu. 5.23 Does Ethereal work on Windows ME? 5.24 Does Ethereal work on Windows XP? 5.25 Why doesn't Ethereal correctly identify RTP packets? It shows them only as UDP. 5.26 Why doesn't Ethereal show Yahoo Messenger packets in captures that contain Yahoo Messenger traffic? 5.27 Why do I get the error Gdk-ERROR **: Palettized display (256-colour) mode not supported on Windows. aborting.... when I try to run Ethereal on Windows? 5.28 When I capture on Windows in promiscuous mode, I can see packets other than those sent to or from my machine; however, those packets show up with a "Short Frame" indication, unlike packets to or from my machine. What should I do to arrange that I see those packets in their entirety? 5.29 How can I capture raw 802.11 packets, including non-data (management, beacon) packets? 5.30 How can I capture packets with CRC errors? 5.31 How can I capture entire frames, including the FCS? 5.32 Ethereal hangs after I stop a capture. 5.33 How can I search for, or filter, packets that have a particular string anywhere in them? GENERAL QUESTIONS Q 1.1: Where can I get help? A: Support is available on the ethereal-users mailing list. Subscription information and archives for all of Ethereal's mailing lists can be found at http://www.ethereal.com/lists Q 1.2: What protocols are currently supported? A: There are currently 381 supported protocols and media, listed below. Descriptions can be found in the ethereal(1) man page. 802.1q Virtual LAN 802.1x Authentication AFS (4.0) Replication Server call declarations AOL Instant Messenger ARCNET ATM ATM AAL1 ATM AAL3/4 ATM LAN Emulation ATM OAM AAL AVS WLAN Capture header Ad hoc On-demand Distance Vector Routing Protocol Address Resolution Protocol Aggregate Server Access Protocol Alert Standard Forum Andrew File System (AFS) Apache JServ Protocol v1.3 AppleTalk Filing Protocol AppleTalk Session Protocol AppleTalk Transaction Protocol packet Appletalk Address Resolution Protocol Application Configuration Access Protocol Async data over ISDN (V.120) Authentication Header BACnet Virtual Link Control Banyan Vines ARP Banyan Vines Echo Banyan Vines Fragmentation Protocol Banyan Vines ICP Banyan Vines IP Banyan Vines IPC Banyan Vines LLC Banyan Vines RTP Banyan Vines SPP Blocks Extensible Exchange Protocol Boardwalk Boot Parameters Bootstrap Protocol Border Gateway Protocol Building Automation and Control Network APDU Building Automation and Control Network NPDU CDS Clerk Server Calls Check Point High Availability Protocol Checkpoint FW-1 Cisco Auto-RP Cisco Discovery Protocol Cisco Group Management Protocol Cisco HDLC Cisco Hot Standby Router Protocol Cisco ISL Cisco Interior Gateway Routing Protocol Cisco NetFlow Cisco SLARP Clearcase NFS CoSine IPNOS L2 debug output Common Open Policy Service Common Unix Printing System (CUPS) Browsing Protocol DCE DFS Calls DCE Distributed Time Service Local Server DCE Distributed Time Service Provider DCE Name Service DCE RPC DCE Security ID Mapper DCE/RPC BOS Server DCE/RPC CDS Solicitation DCE/RPC Conversation Manager DCE/RPC Endpoint Mapper DCE/RPC FLDB DCE/RPC FLDB UBIK TRANSFER DCE/RPC FLDB UBIKVOTE DCE/RPC Kerberos V DCE/RPC RS_ACCT DCE/RPC RS_MISC DCE/RPC RS_UNIX DCE/RPC Remote Management DCE/RPC Repserver Calls DCE/RPC TokenServer Calls DCE/RPC UpServer DCOM OXID Resolver DCOM Remote Activation DEC Spanning Tree Protocol DHCPv6 DNS Control Program Server Data Data Link SWitching Data Stream Interface Datagram Delivery Protocol Diameter Protocol Distance Vector Multicast Routing Protocol Distributed Checksum Clearinghouse Prototocl Domain Name Service Dynamic DNS Tools Protocol Encapsulating Security Payload Enhanced Interior Gateway Routing Protocol Ethernet Ethernet over IP Extensible Authentication Protocol FC Extended Link Svc FC Fabric Configuration Server FCIP FTP Data FTServer Operations Fiber Distributed Data Interface Fibre Channel Fibre Channel Common Transport Fibre Channel Fabric Zone Server Fibre Channel Name Server Fibre Channel Protocol for SCSI Fibre Channel SW_ILS File Transfer Protocol (FTP) Financial Information eXchange Protocol Frame Frame Relay GARP Multicast Registration Protocol GARP VLAN Registration Protocol GPRS Tunneling Protocol GPRS Tunnelling Protocol v0 GPRS Tunnelling Protocol v1 General Inter-ORB Protocol Generic Routing Encapsulation Generic Security Service Application Program Interface Gnutella Protocol HP Extended Local-Link Control HP Remote Maintenance Protocol Hummingbird NFS Daemon HyperSCSI Hypertext Transfer Protocol ICQ Protocol IEEE 802.11 wireless LAN IEEE 802.11 wireless LAN management frame ILMI IP Over FC IP Payload Compression IPX Message IPX Routing Information Protocol IPX WAN ISDN ISDN Q.921-User Adaptation Layer ISDN User Part ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol ISO 8073 COTP Connection-Oriented Transport Protocol ISO 8473 CLNP ConnectionLess Network Protocol ISO 8602 CLTP ConnectionLess Transport Protocol ISO 9542 ESIS Routeing Information Exchange Protocol ITU-T Recommendation H.261 Intel ANS probe Intelligent Platform Management Interface Inter-Access-Point Protocol Interbase Internet Cache Protocol Internet Content Adaptation Protocol Internet Control Message Protocol Internet Control Message Protocol v6 Internet Group Management Protocol Internet Message Access Protocol Internet Printing Protocol Internet Protocol Internet Protocol Version 6 Internet Relay Chat Internet Security Association and Key Management Protocol Internetwork Packet eXchange Java RMI Java Serialization Kerberos Kerberos Administration Kernel Lock Manager Label Distribution Protocol Layer 2 Tunneling Protocol Lightweight Directory Access Protocol Line Printer Daemon Protocol Link Access Procedure Balanced (LAPB) Link Access Procedure Balanced Ethernet (LAPBETHER) Link Access Procedure, Channel D (LAPD) Link Aggregation Control Protocol Link Management Protocol (LMP) Linux cooked-mode capture Local Management Interface LocalTalk Link Access Protocol Logical-Link Control Lucent/Ascend debug output MDS Header MMS Message Encapsulation MS Proxy Protocol MSN Messenger Service MSNIP: Multicast Source Notification of Interest Protocol MTP 2 Transparent Proxy MTP 2 User Adaptation Layer MTP 3 User Adaptation Layer MTP2 Peer Adaptation Layer Message Transfer Part Level 2 Message Transfer Part Level 3 Message Transfer Part Level 3 Management Microsoft Distributed File System Microsoft Exchange MAPI Microsoft Local Security Architecture Microsoft Local Security Architecture (Directory Services) Microsoft Network Logon Microsoft Registry Microsoft Security Account Manager Microsoft Server Service Microsoft Service Control Microsoft Spool Subsystem Microsoft Telephony API Service Microsoft Windows Browser Protocol Microsoft Windows Lanman Remote API Protocol Microsoft Windows Logon Protocol Microsoft Workstation Service Mobile IP Mobile IPv6 Modbus/TCP Mount Service MultiProtocol Label Switching Header Multicast Router DISCovery protocol Multicast Source Discovery Protocol MySQL Protocol NFSACL NFSAUTH NIS+ NIS+ Callback NSPI NTLM Secure Service Provider Name Binding Protocol Name Management Protocol over IPX NetBIOS NetBIOS Datagram Service NetBIOS Name Service NetBIOS Session Service NetBIOS over IPX NetWare Core Protocol NetWare Link Services Protocol Network Data Management Protocol Network File System Network Lock Manager Protocol Network News Transfer Protocol Network Status Monitor CallBack Protocol Network Status Monitor Protocol Network Time Protocol Novell Distributed Print System Null/Loopback Open Shortest Path First OpenBSD Encapsulating device OpenBSD Packet Filter log file PC NFS PPP Bandwidth Allocation Control Protocol PPP Bandwidth Allocation Protocol PPP CDP Control Protocol PPP Callback Control Protocol PPP Challenge Handshake Authentication Protocol PPP Compressed Datagram PPP Compression Control Protocol PPP IP Control Protocol PPP IPv6 Control Protocol PPP Link Control Protocol PPP MPLS Control Protocol PPP Multilink Protocol PPP Multiplexing PPP Password Authentication Protocol PPP VJ Compression PPP-over-Ethernet Discovery PPP-over-Ethernet Session PPPMux Control Protocol Point-to-Point Protocol Point-to-Point Tunnelling Protocol Portmap Post Office Protocol Pragmatic General Multicast Prism Privilege Server operations Protocol Independent Multicast Q.2931 Q.931 Quake II Network Protocol Quake III Arena Network Protocol Quake Network Protocol QuakeWorld Network Protocol Qualified Logical Link Control RFC 2250 MPEG1 RIPng RPC Browser RSTAT RSYNC File Synchroniser RX Protocol Radio Access Network Application Part Radius Protocol Raw packet data Real Time Streaming Protocol Real-Time Transport Protocol Real-time Transport Control Protocol Registry Server Attributes Manipulation Interface Registry server administration operations. Remote Management Control Protocol Remote Override interface Remote Procedure Call Remote Program Load Remote Quota Remote Shell Remote Wall protocol Remote sec_login preauth interface. Resource ReserVation Protocol (RSVP) Rlogin Protocol Routing Information Protocol Routing Table Maintenance Protocol SADMIND SCSI SGI Mount Service SMB (Server Message Block Protocol) SMB MailSlot Protocol SMB Pipe Protocol SNA-over-Ethernet SNMP Multiplex Protocol SPNEGO-KRB5 SPRAY SS7 SCCP-User Adaptation Layer SSCOP SSH Protocol Secure Socket Layer Sequenced Packet eXchange Service Advertisement Protocol Service Location Protocol Session Announcement Protocol Session Description Protocol Session Initiation Protocol Short Message Peer to Peer Signalling Connection Control Part Signalling Connection Control Part Management Simple Mail Transfer Protocol Simple Network Management Protocol Sinec H1 Protocol Skinny Client Control Protocol SliMP3 Communication Protocol Socks Protocol Spanning Tree Protocol Spnego Stream Control Transmission Protocol Synchronous Data Link Control (SDLC) Syslog message Systems Network Architecture Systems Network Architecture XID TACACS TACACS+ TPKT Tabular Data Stream Tazmen Sniffer Protocol Telnet Time Protocol Time Synchronization Protocol Token-Ring Token-Ring Media Access Control Transmission Control Protocol Transparent Network Substrate Protocol Trivial File Transfer Protocol Universal Computer Protocol User Datagram Protocol Virtual Router Redundancy Protocol Virtual Trunking Protocol WAP Binary XML Web Cache Coordination Protocol Wellfleet Breath of Life Wellfleet Compression Wellfleet HDLC Who Windows 2000 DNS Wireless Session Protocol Wireless Transaction Protocol Wireless Transport Layer Security X Display Manager Control Protocol X.25 X.25 over TCP X.29 X11 Xyplex Yahoo Messenger Protocol Yahoo YMSG Messenger Protocol Yellow Pages Bind Yellow Pages Passwd Yellow Pages Service Yellow Pages Transfer Zebra Protocol Zone Information Protocol iSCSI iSNS Q 1.3: Are there any plans to support {your favorite protocol}? A: Support for particular protocols is added to Ethereal as a result of people contributing that support; no formal plans for adding support for particular protocols in particular future releases exist. Q 1.4: Can Ethereal read capture files from {your favorite network analyzer}? A: Support for particular protocols is added to Ethereal as a result of people contributing that support; no formal plans for adding support for particular protocols in particular future releases exist. If a network analyzer writes out files in a format already supported by Ethereal (e.g., in libpcap format), Ethereal may already be able to read them, unless the analyzer has added its own proprietary extensions to that format. If a network analyzer writes out files in its own format, or has added proprietary extensions to another format, in order to make Ethereal read captures from that network analyzer, we would either have to have a specification for the file format, or the extensions, sufficient to give us enough information to read the parts of the file relevant to Ethereal, or would need at least one capture file in that format AND a detailed textual analysis of the packets in that capture file (showing packet time stamps, packet lengths, and the top-level packet header) in order to reverse-engineer the file format. Note that there is no guarantee that we will be able to reverse-engineer a capture file format. Q 1.5: What devices can Ethereal use to capture packets? A: Ethereal can read live data from Ethernet, Token-Ring, FDDI, serial (PPP and SLIP) (if the OS on which it's running allows Ethereal to do so), 802.11 wireless LAN (if the OS on which it's running allows Ethereal to do so), ATM connections (if the OS on which it's running allows Ethereal to do so), and the "any" device supported on Linux by recent versions of libpcap. See the list of supported capture media on various OSes for details (several items in there say "Unknown", which doesn't mean "Ethereal can't capture on them", it means "we don't know whether it can capture on them"; we expect that it will be able to capture on many of them, but we haven't tried it ourselves - if you try one of those types and it works, please send an update to ethereal-web[AT]ethereal.com). It can also read a variety of capture file formats, including: * libpcap/tcpdump * Sun snoop/atmsnoop * Shomiti/Finisar Surveyor * LanAlyzer * DOS-based Sniffer (compressed and uncompressed) * MS Network Monitor * AIX iptrace * NetXray and Windows-based Sniffer * EtherPeek/TokenPeek/AiroPeek * RADCOM WAN/LAN analyzer * Lucent/Ascend debug output * Toshiba ISDN router "snoop" output * HPUX nettl * ISDN4BSD "i4btrace" utility. * Cisco Secure IDS * pppd log files (pppdump format) * VMS TCPIPtrace * DBS Etherwatch * Visual Networks' Visual UpTime * CoSine L2 debug so that it can read traces from various network types, as captured by other applications or equipment, even if it cannot itself capture on those network types. Q 1.6: How do you pronounce Ethereal? Where did the name come from? A: The English pronunciation can be found in Merriam-Webster's online dictionary at http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=ethereal. According to the book "Computer Networks" by Andrew Tannenbaum, Ethernet was named after the "luminiferous ether" which was once thought to carry electromagnetic radiation. Taking that into consideration, Ethereal seemed like an appropriate name for an Ethernet sniffer. DOWNLOADING ETHEREAL Q 2.1: I downloaded the Win32 installer, but when I try to run it, I get an error. A: The program you used to download it may have downloaded it incorrectly. Web browsers sometimes may do this. Try downloading it with, for example: * Wget, for which Windows binaries are available on the SunSITE FTP server at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI offers a GUI interface that uses wget; * WS_FTP from Ipswitch, * the ftp command that comes with Windows. If you use the ftp command, make sure you do the transfer in binary mode rather than ASCII mode, by using the binary command before transferring the file. Q 2.2: When I try to download the WinPcap driver and library, I can't get to the WinPcap Web site. A: As is the case with all Web sites, that site won't necessarily always be accessible; the server may be down due to a problem or down for maintenance, or there may be a networking problem between you and the server. You should try again later, or try the local mirror or the Wiretapped.net mirror. INSTALLING ETHEREAL Q 3.1: I installed an Ethereal RPM, but Ethereal doesn't seem to be installed; only Tethereal is installed. A: Red Hat RPMs for Ethereal put only the non-GUI components into the ethereal RPM, the fact that Ethereal is a GUI program nonwithstanding; there's a separate ethereal-gnome RPM that includes GUI components such as Ethereal itself, the fact that Ethereal doesn't use GNOME nonwithstanding. Find the ethereal-gnome RPM, and install that also. BUILDING ETHEREAL Q 4.1: The configure script can't find pcap.h or bpf.h, but I have libpcap installed. A: Are you sure pcap.h and bpf.h are installed? The official distribution of libpcap only installs the libpcap.a library file when "make install" is run. To install pcap.h and bpf.h, you must run "make install-incl". If you're running Debian or Redhat, make sure you have the "libpcap-dev" or "libpcap-devel" packages installed. It's also possible that pcap.h and bpf.h have been installed in a strange location. If this is the case, you may have to tweak aclocal.m4. Q 4.2: Why do I get the error dftest_DEPENDENCIES was already defined in condition TRUE, which implies condition HAVE_PLUGINS_TRUE when I try to build Ethereal from CVS or a CVS snapshot? A: You probably have automake 1.5 installed on your machine (the command automake --version will report the version of automake on your machine). There is a bug in that version of automake that causes this problem; upgrade to a later version of automake (1.6 or later). Q 4.3: The link fails with a number of "Output line too long." messages followed by linker errors. A: The version of the sed command on your system is incapable of handling very long lines. On Solaris, for example, /usr/bin/sed has a line length limit too low to allow libtool to work; /usr/xpg4/bin/sed can handle it, as can GNU sed if you have it installed. On Solaris, changing your command search path to search /usr/xpg4/bin before /usr/bin should make the problem go away; on any platform on which you have this problem, installing GNU sed and changing your command path to search the directory in which it is installed before searching the directory with the version of sed that came with the OS should make the problem go away. Q 4.4: The link fails on Solaris because plugin_list is undefined. A: This appears to be due to a problem with some versions of the GTK+ and GLib packages from www.sunfreeware.org; un-install those packages, and try getting the 1.2.10 versions from that site, or the versions from The Written Word, or the versions from Sun's GNOME distribution, or the versions from the supplemental software CD that comes with the Solaris media kit, or build them from source from the GTK Web site. Then re-run the configuration script, and try rebuilding Ethereal. (If you get the 1.2.10 versions from www.sunfreeware.org, and the problem persists, un-install them and try installing one of the other versions mentioned.) Q 4.5: The build fails on Windows because of conflicts between winsock.h and winsock2.h. A: As of Ethereal 0.9.5, you must install WinPcap 2.3 or later, and the corresponding version of the developer's pack, in order to be able to compile Ethereal; it will not compile with older versions of the developer's pack. The symptoms of this failure are conflicts between definitions in winsock.h and in winsock2.h; Ethereal uses winsock2.h, but pre-2.3 versions of the WinPcap developer's packet use winsock.h. (2.3 uses winsock2.h, so if Ethereal were to use winsock.h, it would not be able to build with current versions of the WinPcap developer's pack.) Note that the installed version of the developer's pack should be the same version as the version of WinPcap you have installed. USING ETHEREAL Q 5.1: When I use Ethereal to capture packets, I see only packets to and from my machine, or I'm not seeing all the traffic I'm expecting to see from or to the machine I'm trying to monitor. A: This might be because the interface on which you're capturing is plugged into a switch; on a switched network, unicast traffic between two ports will not necessarily appear on other ports - only broadcast and multicast traffic will be sent to all ports. Note that even if your machine is plugged into a hub, the "hub" may be a switched hub, in which case you're still on a switched network. Note also that on the Linksys Web site, they say that their auto-sensing hubs "broadcast the 10Mb packets to the port that operate at 10Mb only and broadcast the 100Mb packets to the ports that operate at 100Mb only", which would indicate that if you sniff on a 10Mb port, you will not see traffic coming sent to a 100Mb port, and vice versa. This problem has also been reported for Netgear dual-speed hubs, and may exist for other "auto-sensing" or "dual-speed" hubs. Some switches have the ability to replicate all traffic on all ports to a single port so that you can plug your sniffer into that single port to sniff all traffic. You would have to check the documentation for the switch to see if this is possible and, if so, to see how to do this. See, for example: * this documentation from Cisco on the Switched Port Analyzer (SPAN) feature on Catalyst switches; * documentation from HP on how to set "monitoring"/"mirroring" on ports on the console for HP Advancestack Switch 208 and 224; * the "Network Monitoring Port Features" section of chapter 6 of documentation from HP for HP ProCurve Switches 1600M, 2424M, 4000M, and 8000M. Note also that many firewall/NAT boxes have a switch built into them; this includes many of the "cable/DSL router" boxes. If you have a box of that sort, that has a switch with some number of Ethernet ports into which you plug machines on your network, and another Ethernet port used to connect to a cable or DSL modem, you can, at least, sniff traffic between the machines on your network and the Internet by plugging the Ethernet port on the router going to the modem, the Ethernet port on the modem, and the machine on which you're running Ethereal into a hub (make sure it's not a switching hub, and that, if it's a dual-speed hub, all three of those ports are running at the same speed. If your machine is not plugged into a switched network or a dual-speed hub, or it is plugged into a switched network but the port is set up to have all traffic replicated to it, the problem might be that the network interface on which you're capturing doesn't support "promiscuous" mode, or because your OS can't put the interface into promiscuous mode. Normally, network interfaces supply to the host only: * packets sent to one of that host's link-layer addresses; * broadcast packets; * multicast packets sent to a multicast address that the host has configured the interface to accept. Most network interfaces can also be put in "promiscuous" mode, in which they supply to the host all network packets they see. Ethereal will try to put the interface on which it's capturing into promiscuous mode unless the "Capture packets in promiscuous mode" option is turned off in the "Capture Options" dialog box, and Tethereal will try to put the interface on which it's capturing into promiscuous mode unless the -p option was specified. However, some network interfaces don't support promiscuous mode, and some OSes might not allow interfaces to be put into promiscuous mode. If the interface is not running in promiscuous mode, it won't see any traffic that isn't intended to be seen by your machine. It will see broadcast packets, and multicast packets sent to a multicast MAC address the interface is set up to receive. You should ask the vendor of your network interface whether it supports promiscuous mode. If it does, you should ask whoever supplied the driver for the interface (the vendor, or the supplier of the OS you're running on your machine) whether it supports promiscuous mode with that network interface. In the case of token ring interfaces, the drivers for some of them, on Windows, may require you to enable promiscuous mode in order to capture in promiscuous mode. Ask the vendor of the card how to do this, or see, for example, this information on promiscuous mode on some Madge token ring adapters (note that those cards can have promiscuous mode disabled permanently, in which case you can't enable it). In the case of wireless LAN interfaces, it appears that, when those interfaces are promiscuously sniffing, they're running in a significantly different mode from the mode that they run in when they're just acting as network interfaces (to the extent that it would be a significant effor for those drivers to support for promiscuously sniffing and acting as regular network interfaces at the same time), so it may be that Windows drivers for those interfaces don't support promiscuous mode. Q 5.2: I can't see any TCP packets other than packets to and from my machine, even though another sniffer on the network sees those packets. A: You're probably not seeing any packets other than unicast packets to or from your machine, and broadcast and multicast packets; a switch will normally send to a port only unicast traffic sent to the MAC address for the interface on that port, and broadcast and multicast traffic - it won't send to that port unicast traffic sent to a MAC address for some other interface - and a network interface not in promiscuous mode will receive only unicast traffic sent to the MAC address for that interface, broadcast traffic, and multicast traffic sent to a multicast MAC address the interface is set up to receive. TCP doesn't use broadcast or multicast, so you will only see your own TCP traffic, but UDP services may use broadcast or multicast so you'll see some UDP traffic - however, this is not a problem with TCP traffic, it's a problem with unicast traffic, as you also won't see all UDP traffic between other machines. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.3: I'm only seeing ARP packets when I try to capture traffic. A: You're probably on a switched network, and running Ethereal on a machine that's not sending traffic to the switch and not being sent any traffic from other machines on the switch. ARP packets are often broadcast packets, which are sent to all switch ports. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.4: How do I put an interface into promiscuous mode? A: By not disabling promiscuous mode when running Ethereal or Tethereal. Note, however, that: * the form of promiscuous mode that libpcap (the library that programs such as tcpdump, Ethereal, etc. use to do packet capture) turns on will not necessarily be shown if you run ifconfig on the interface on a UNIX system; * some network interfaces might not support promiscuous mode, and some drivers might not allow promiscuous mode to be turned on - see this earlier question for more information on that; * the fact that you're not seeing any traffic, or are only seeing broadcast traffic, or aren't seeing any non-broadcast traffic other than traffic to or from the machine running Ethereal, does not mean that promiscuous mode isn't on - see this earlier question for more information on that. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.5: I can set a display filter just fine, but capture filters don't work. A: Capture filters currently use a different syntax than display filters. Here's the corresponding section from the ethereal(1) man page: "Display filters in Ethereal are very powerful; more fields are filterable in Ethereal than in other protocol analyzers, and the syntax you can use to create your filters is richer. As Ethereal progresses, expect more and more protocol fields to be allowed in display filters. Packet capturing is performed with the pcap library. The capture filter syntax follows the rules of the pcap library. This syntax is different from the display filter syntax." The capture filter syntax used by libpcap can be found in the tcpdump(8) man page. Q 5.6: I'm entering valid capture filters, but I still get "parse error" errors. A: There is a bug in some versions of libpcap/WinPcap that cause it to report parse errors even for valid expressions if a previous filter expression was invalid and got a parse error. Try exiting and restarting Ethereal; if you are using a version of libpcap/WinPcap with this bug, this will "erase" its memory of the previous parse error. If the capture filter that got the "parse error" now works, the earlier error with that filter was probably due to this bug. The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of libpcap have this bug, but 0.6[.x] and later versions don't. Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and doesn't have this bug. If you are running Ethereal on a UNIX-flavored platform, run "ethereal -v", or select "About Ethereal..." from the "Help" menu in Ethereal, to see what version of libpcap it's using. If it's not 0.6 or later, you will need either to upgrade your OS to get a later version of libpcap, or will need to build and install a later version of libpcap from the tcpdump.org Web site and then recompile Ethereal from source with that later version of libpcap. If you are running Ethereal on Windows with a pre-2.3 version of WinPcap, you will need to un-install WinPcap and then download and install WinPcap 2.3. Q 5.7: I saved a filter and tried to use its name to filter the display, but I got an "Unexpected end of filter string" error. A: You cannot use the name of a saved display filter as a filter. To filter the display, you can enter a display filter expression - not the name of a saved display filter - in the "Filter:" box at the bottom of the display, and type the key or press the "Apply" button (that does not require you to have a saved filter), or, if you want to use a saved filter, you can press the "Filter:" button, select the filter in the dialog box that pops up, and press the "OK" button. Q 5.8: Why am I seeing lots of packets with incorrect TCP checksums? A: If the packets that have incorrect TCP checksums are all being sent by the machine on which Ethereal is running, this is probably because the network interface on which you're capturing does TCP checksum offloading. That means that the TCP checksum is added to the packet by the network interface, not by the OS's TCP/IP stack; when capturing on an interface, packets being sent by the host on which you're capturing are directly handed to the capture interface by the OS, which means that they are handed to the capture interface without a TCP checksum being added to them. The only way to prevent this from happening would be to disable TCP checksum offloading, but 1. that might not even be possible on some OSes; 2. that could reduce networking performance significantly. However, you can disable the check that Ethereal does of the TCP checksum, so that it won't report any packets as having TCP checksum errors, and so that it won't refuse to do TCP reassembly due to a packet having an incorrect TCP checksum. That can be set as an Ethereal preference by selecting "Preferences" from the "Edit" menu, opening up the "Protocols" list in the left-hand pane of the "Preferences" dialog box, selecting "TCP", from that list, turning off the "Check the validity of the TCP checksum when possible" option, clicking "Save" if you want to save that setting in your preference file, and clicking "OK". It can also be set on the Ethereal or Tethereal command line with a -o tcp.check_checksum:false command-line flag, or manually set in your preferences file by adding a tcp.check_checksum:false line. Q 5.9: I've just installed Ethereal, and the traffic on my local LAN is boring. A: We have a collection of strange and exotic sample capture files at http://www.ethereal.com/sample/ Q 5.10: When I run Ethereal on Solaris 8, it dies with a Bus Error when I start it. A: Some versions of the GTK+ library from www.sunfreeware.org appear to be buggy, causing Ethereal to drop core with a Bus Error. Un-install those packages, and try getting the 1.2.10 version from that site, or the version from The Written Word, or the version from Sun's GNOME distribution, or the version from the supplemental software CD that comes with the Solaris media kit, or build it from source from the GTK Web site. Update the GLib library to the 1.2.10 version, from the same source, as well. (If you get the 1.2.10 versions from www.sunfreeware.org, and the problem persists, un-install them and try installing one of the other versions mentioned.) Similar problems may exist with older versions of GTK+ for earlier versions of Solaris. Q 5.11: When I try to run Ethereal, it complains about sprint_realloc_objid being undefined. A: Ethereal can only be linked with version 4.2.2 or later of UCD SNMP. Your version of Ethereal was dynamically linked with such a version of UCD SNMP; however, you have an older version of UCD SNMP installed, which means that when Ethereal is run, it tries to link to the older version, and fails. You will have to replace that version of UCD SNMP with version 4.2.2 or a later version. Q 5.12: I'm running Ethereal on Linux; why do my time stamps have only 100ms resolution, rather than 1us resolution? A: Ethereal gets time stamps from libpcap/WinPcap, and libpcap/WinPcap get them from the OS kernel, so Ethereal - and any other program using libpcap, such as tcpdump - is at the mercy of the time stamping code in the OS for time stamps. At least on x86-based machines, Linux can get high-resolution time stamps on newer processors with the Time Stamp Counter (TSC) register; for example, Intel x86 processors, starting with the Pentium Pro, and including all x86 processors since then, have had a TSC, and other vendors probably added the TSC at some point to their families of x86 processors. The Linux kernel must be configured with the CONFIG_X86_TSC option enabled in order to use the TSC. Make sure this option is enabled in your kernel. In addition, some Linux distributions may have bugs in their versions of the kernel that cause packets not to be given high-resolution time stamps even if the TSC is enabled. See, for example, bug 61111 for Red Hat Linux 7.2. If your distribution has a bug such as this, you may have to run a standard kernel from kernel.org in order to get high-resolution time stamps. Q 5.13: I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why are the time stamps on packets wrong? A: This is due to a bug in WinPcap. The bug should be fixed in WinPcap 3.0. Q 5.14: When I try to run Ethereal on Windows, it fails to run because it can't find packet.dll. A: In older versions of Ethereal, there were two binary distributions available for Windows, one that supported capturing packets, and one that didn't. The version that supported capturing packets required that you install the WinPcap driver; if you didn't install it, it would fail to run because it couldn't find packet.dll. The current version of Ethereal has only one binary distribution for Windows; that version will check whether WinPcap is installed and, if it's not, will disable support for packet capture. The WinPcap driver and libraries can be downloaded from the WinPcap Web site, the local mirror of the WinPcap Web site, or the Wiretapped.net mirror of the WinPcap site. Q 5.15: I'm running Ethereal on Windows; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? A: If you are running Ethereal on Windows NT 4.0, Windows 2000, Windows XP, or Windows Server, and this is the first time you have run a WinPcap-based program (such as Ethereal, or Tethereal, or WinDump, or Analyzer, or...) since the machine was rebooted, you need to run that program from an account with administrator privileges; once you have run such a program, you will not need administrator privileges to run any such programs until you reboot. If you are running on Windows 95/98/Me, or if you are running on Windows NT 4.0/2000/XP/Server and have administrator privileges or a WinPcap program has been run with those privileges since the machine rebooted, then note that Ethereal relies on the WinPcap library, on the WinPcap device driver, and on the facilities that come with the OS on which it's running in order to do captures. Therefore, if the OS, the WinPcap library, or the WinPcap driver don't support capturing on a particular network interface device, Ethereal won't be able to capture on that device. Note that: * 2.02 and earlier versions of the WinPcap driver and library that Ethereal uses for packet capture didn't support Token Ring interfaces; the current version, 2.3, does support Token Ring, and the current version of Ethereal works with (and, in fact, requires) WinPcap 2.1 or later. If you are having problems capturing on Token Ring interfaces, and you have WinPcap 2.02 or an earlier version of WinPcap installed, you should uninstall WinPcap, download and install the current version of WinPcap, and then install the latest version of Ethereal. * On Windows 95, 98, or Me, sometimes more than one interface will be given the same name; if that is the case, you will only be able to capture on one of those interfaces - it's not clear to which one the name, when used in a WinPcap application, will refer. For example, if you have a PPP serial interface and a VPN interface, they might show up with the same name, for example "ppp-mac", and if you try to capture on "ppp-mac", it might not capture on the interface you're currently using. In that case, you might, for example, have to remove the VPN interface from the system in order to capture on the PPP serial interface. * WinPcap doesn't support PPP WAN interfaces on Windows NT/2000/XP/Server, so Ethereal cannot capture packets on those devices when running on Windows NT/2000/XP/Server. Regular dial-up lines, ISDN lines, and various other lines such as T1/E1 lines are all PPP interfaces. This may cause the interface not to show up on the list of interfaces in the "Capture Options" dialog. * WinPcap prior to 3.0 does not support multiprocessor machines (note that machines with a single multi-threaded processor, such as Intel's new multi-threaded x86 processors, are multiprocessor machines as far as the OS and WinPcap are concerned), and recent 2.x versions of WinPcap refuse to operate if they detect that they're running on a multiprocessor machine, which means that they may not show any network interfaces. You will need to use WinPcap 3.0 to capture on a multiprocessor machine. If an interface doesn't show up in the list of interfaces in the "Interface:" field, and you know the name of the interface, try entering that name in the "Interface:" field and capturing on that device. If the attempt to capture on it succeeds, the interface is somehow not being reported by the mechanism Ethereal uses to get a list of interfaces; please report this to ethereal-dev@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system; * the type of network device you're using. If you are having trouble capturing on a particular network interface, and you've made sure that (on platforms that require it) you've arranged that packet capture support is present, as per the above, first try capturing on that device with WinDump; see the WinDump Web site or the local mirror of the WinDump Web site for information on using WinDump. If you can capture on the interface with WinDump, send mail to ethereal-users@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system; * the type of network device you're using; * the error message you get from Ethereal. If you cannot capture on the interface with WinDump, this is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the WinPcap library and/or the WinPcap device driver; so first check the WinPcap FAQ, the local mirror of that FAQ, or the Wiretapped.net mirror of that FAQ, to see if your problem is mentioned there. If not, then see the WinPcap support page (or the local mirror of that page) - check the "Submitting bugs" section. You may also want to ask the ethereal-users@ethereal.com and the winpcap-users@winpcap.polito.it mailing lists to see if anybody happens to know about the problem and know a workaround or fix for the problem. (Note that you will have to subscribe to that list in order to be allowed to mail to it; see the WinPcap support page, or the local mirror of that page, for information on the mailing list.) In your mail, please give full details of the problem, as described above, and also indicate that the problem occurs with WinDump, not just with Ethereal. Q 5.16: I'm running on a UNIX-flavored OS; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? A: You may need to run Ethereal from an account with sufficient privileges to capture packets, such as the super-user account. Only those interfaces that Ethereal can open for capturing show up in that list; if you don't have sufficient privileges to capture on any interfaces, no interfaces will show up in the list. If you are running Ethereal from an account with sufficient privileges, then note that Ethereal relies on the libpcap library, and on the facilities that come with the OS on which it's running in order to do captures. Therefore, if the OS or the libpcap library don't support capturing on a particular network interface device, Ethereal won't be able to capture on that device. On Linux, note that you need to have "packet socket" support enabled in your kernel; see the "Packet socket" item in the Linux "Configure.help" file. On BSD, note that you need to have BPF support enabled in your kernel; see the documentation for your system for information on how to enable BPF support (if it's not enabled by default on your system). On DEC OSF/1, Digital UNIX, or Tru64 UNIX, note that you need to have packet filtering support in your kernel; the doconfig command will allow you to configure and build a new kernel with that option. On Solaris, note that libpcap 0.6.2 and earlier didn't support Token Ring interfaces; the current version, 0.7.2, does support Token Ring, and the current version of Ethereal works with libcap 0.7.2 and later. If an interface doesn't show up in the list of interfaces in the "Interface:" field, and you know the name of the interface, try entering that name in the "Interface:" field and capturing on that device. If the attempt to capture on it succeeds, the interface is somehow not being reported by the mechanism Ethereal uses to get a list of interfaces; please report this to ethereal-dev@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system (for Linux, give both the version number of the kernel and the name and version number of the distribution you're using); * the type of network device you're using. If you are having trouble capturing on a particular network interface, and you've made sure that (on platforms that require it) you've arranged that packet capture support is present, as per the above, first try capturing on that device with tcpdump. If you can capture on the interface with tcpdump, send mail to ethereal-users@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system (for Linux, give both the version number of the kernel and the name and version number of the distribution you're using); * the type of network device you're using; * the error message you get from Ethereal. If you cannot capture on the interface with tcpdump, this is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the libpcap library; so you should report the problem to the company or organization that produces the OS (in the case of a Linux distribution, report the problem to whoever produces the distribution). You may also want to ask the ethereal-users@ethereal.com and the tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to know about the problem and know a workaround or fix for the problem. In your mail, please give full details of the problem, as described above, and also indicate that the problem occurs with tcpdump not just with Ethereal. Q 5.17: I'm running Ethereal on Windows NT/2000/XP/Server; my machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the "Interface" item in the "Capture Options" dialog box. Why can no packets be sent on or received from that network while I'm trying to capture traffic on that interface? A: WinPcap doesn't support PPP WAN interfaces on Windows NT/2000/XP/Server; one symptom that may be seen is that attempts to capture in promiscuous mode on the interface cause the interface to be incapable of sending or receiving packets. You can disable promiscuous mode using the -p command-line flag or the item in the "Capture Preferences" dialog box, but this may mean that outgoing packets, or incoming packets, won't be seen in the capture. Q 5.18: I'm running Ethereal on Windows 95/98/Me, on a machine with more than one network adapter of the same type; Ethereal shows all of those adapters with the same name, but I can't use any of those adapters other than the first one. A: Unfortunately, Windows 95/98/Me gives the same name to multiple instances of the type of same network adapter. Therefore, WinPcap cannot distinguish between them, so a WinPcap-based application can capture only on the first such interface; Ethereal is a libpcap/WinPcap-based application. Q 5.19: I'm running Ethereal on Windows, and I'm not seeing any traffic being sent by the machine running Ethereal. A: If you are running some form of VPN client software, it might be causing this problem; people have seen this problem when they have Check Point's VPN software installed on their machine. If that's the cause of the problem, you will have to remove the VPN software in order to have Ethereal (or any other application using WinPcap) see outgoing packets; unfortunately, neither we nor the WinPcap developers know any way to make WinPcap and the VPN software work well together. Q 5.20: I'm trying to capture traffic but I'm not seeing any. A: Is the machine running Ethereal sending out any traffic on the network interface on which you're capturing, or receiving any traffic on that network, or is there any broadcast traffic on the network or multicast traffic to a multicast group to which the machine running Ethereal belongs? If not, this may just be a problem with promiscuous sniffing, either due to running on a switched network or a dual-speed hub, or due to problems with the interface not supporting promiscuous mode; see the response to this earlier question. Otherwise, on Windows, see the response to this question and, on a UNIX-flavored OS, see the response to this question. Q 5.21: I have an XXX network card on my machine; if I try to capture on it, my machine crashes or resets itself. A: This is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the libpcap/WinPcap library and, if this is Windows, the WinPcap device driver; so: * if you are using Windows, see the WinPcap support page (or the local mirror of that page) - check the "Submitting bugs" section; * if you are using some Linux distribution, some version of BSD, or some other UNIX-flavored OS, you should report the problem to the company or organization that produces the OS (in the case of a Linux distribution, report the problem to whoever produces the distribution). Q 5.22: My machine crashes or resets itself when I select "Start" from the "Capture" menu or select "Preferences" from the "Edit" menu. A: Both of those operations cause Ethereal to try to build a list of the interfaces that it can open; it does so by getting a list of interfaces and trying to open them. There is probably an OS, driver, or, for Windows, WinPcap bug that causes the system to crash when this happens; see the previous question. Q 5.23: Does Ethereal work on Windows ME? A: Yes, but if you want to capture packets, you will need to install the latest version of WinPcap, as 2.02 and earlier versions of WinPcap didn't support Windows ME. You should also install the latest version of Ethereal as well. Q 5.24: Does Ethereal work on Windows XP? A: Yes, but if you want to capture packets, you will need to install the latest version of WinPcap, as 2.2 and earlier versions of WinPcap didn't support Windows XP. Q 5.25: Why doesn't Ethereal correctly identify RTP packets? It shows them only as UDP. A: Ethereal can identify a UDP datagram as containing a packet of a particular protocol running atop UDP only if 1. The protocol in question has a particular standard port number, and the UDP source or destination port number is that port 2. Packets of that protocol can be identified by looking for a "signature" of some type in the packet - i.e., some data that, if Ethereal finds it in some particular part of a packet, means that the packet is almost certainly a packet of that type. 3. Some other traffic earlier in the capture indicated that, for example, UDP traffic between two particular addresses and ports will be RTP traffic. RTP doesn't have a standard port number, so 1) doesn't work; it doesn't, as far as I know, have any "signature", so 2) doesn't work. That leaves 3). If there's RTSP traffic that sets up an RTP session, then, at least in some cases, the RTSP dissector will set things up so that subsequent RTP traffic will be identified. Currently, that's the only place we do that; there may be other places. However, there will always be places where Ethereal is simply incapable of deducing that a given UDP flow is RTP; a mechanism would be needed to allow the user to specify that a given conversation should be treated as RTP. As of Ethereal 0.8.16, such a mechanism exists; if you select a UDP or TCP packet, the right mouse button menu will have a "Decode As..." menu item, which will pop up a dialog box letting you specify that the source port, the destination port, or both the source and destination ports of the packet should be dissected as some particular protocol. Q 5.26: Why doesn't Ethereal show Yahoo Messenger packets in captures that contain Yahoo Messenger traffic? A: Ethereal only recognizes as Yahoo Messenger traffic packets to or from TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP segments that start with the middle of a Yahoo Messenger packet that takes more than one TCP segment will not be recognized as Yahoo Messenger packets (even if the TCP segment also contains the beginning of another Yahoo Messenger packet). Q 5.27: Why do I get the error Gdk-ERROR **: Palettized display (256-colour) mode not supported on Windows. aborting.... when I try to run Ethereal on Windows? A: Ethereal is built using the GTK+ toolkit, which supports most UNIX-flavored OSes, and also supports Windows; that toolkit doesn't support 256-color mode on Windows - it requires HiColor (16-bit colors) or more. If your display supports more than 256 colors, switch to a display mode with more colors; if it doesn't support more than 256 colors, you will be unable to run Ethereal. Q 5.28: When I capture on Windows in promiscuous mode, I can see packets other than those sent to or from my machine; however, those packets show up with a "Short Frame" indication, unlike packets to or from my machine. What should I do to arrange that I see those packets in their entirety? A: In at least some cases, this appears to be the result of PGPnet running on the network interface on which you're capturing; turn it off on that interface. Q 5.29: How can I capture raw 802.11 packets, including non-data (management, beacon) packets? A: That would require that your 802.11 interface run in the mode called "monitor mode" or "RFMON mode". Not all operating systems support that and, even on operating systems that do support it, not all drivers, and thus not all cards, support it. Cisco Aironet cards: The only platforms that allow Ethereal to capture raw 802.11 packets on Cisco Aironet cards are: * Linux, with a 2.4.6 or later kernel; * FreeBSD 4.6 or later, as the driver in FreeBSD 4.5 has bugs that cause packets not to be captured correctly, and the driver in releases prior to 4.5 didn't support capturing raw packets. On FreeBSD, the ancontrol utility must be used; do not enable the full Aironet header via BPF, as Ethereal doesn't currently support that. On Linux with the driver in the 2.4.6 through 2.4.19 kernel, you will need to do echo "Mode: rfmon" >/proc/driver/aironet/ethN/Config if your Aironet card is ethN. To capture traffic from any BSS, do echo "Mode: y" >/proc/driver/aironet/ethN/Config and to return to the normal mode, do echo "Mode: ess" >/proc/driver/aironet/ethN/Config On Linux with the driver in the 2.4.20 kernel, or with the CVS drivers from the airo-linux SourceForge site, you will have to capture on the wifiN interface if your Aironet card is ethN, after running the commands listed above. In all of those cases, Ethereal would have to be linked with libpcap 0.7.1 or later; this means that most Ethereal binary packages won't work unless they're statically linked with libpcap 0.7.1 or later, or they're dynamically linked with libpcap and your system has a libpcap 0.7.1 or later shared library installed (note that libpcap source package from tcpdump.org does not build shared libraries). Some binary packaging mechanisms might make it difficult to install Ethereal binary packages built to depend on older libpcap binary packages if you have a newer libpcap binary package installed; the installer programs for those packaging mechanisms might support disabling dependency checking so that they will install Ethereal even though a newer version of libpcap is installed. Cards using the Prism II chip set (see this page of Linux 802.11 information for details on wireless cards, including information on the chips they use): You can capture raw 802.11 packets with Prism II cards on Linux systems with the 0.1.14-pre6 or later version of the linux-wlan-ng drivers (see the linux-wlan page, and the linux-wlan-ng tarball directory). Those require either Solomon Peachy's patch to libpcap 0.7.1 (see his libpcap-0.7.1-prism.diff file, or his RPMs of that version of libpcap), or the current CVS version of libpcap, which includes his patch (download it from the "Current Tar files" section of the tcpdump.org Web site). If you apply his patches to libpcap 0.7.1 and rebuild and install libpcap, or if you build and install the current CVS version of libpcap, you would have to rebuild Ethereal from source, linking it with that new version of libpcap; an Ethereal binary package would not work. Ethereal binary packages might work if you install the libpcap-0.7.1-1prism.i386.rpm RPM, as it might install a libpcap shared library in place of the one on your system. You may have to run a command to put the interface into monitor mode, or to change other interface settings, and you might have to capture on a wlanN interface rather than a ethN interface, in order to capture raw 802.11 packets. The interface settings are available in your wlan-ng.conf file. See the wlan-ng FAQ for additional information. On other platforms, capturing raw 802.11 packets on Prism II cards is not currently supported. Orinoco Silver and Gold cards: On Linux systems, there are patches on the Orinoco Monitor Mode Patch Page that should allow you to do capture raw 802.11 packets. You will have to determine which version of the driver you have, and select the appropriate patch. Note that the page indicates that not all versions of the Orinoco firmware support this patch. It says, for some versions of the patch, "This patch should allow monitor mode with v8.10 firmware (untested w/ 8.42);" if you have version 8.10 or later firmware on your Orinoco cards, you might have to use those patches, with the corresponding versions of the Orinoco driver, in order to run in monitor mode. That patch is written for the drivers included with the pcmcia-cs drivers, but works equally well for the Orinoco drivers provided with Linux kernels up to 2.4.20. To apply a patch to your kernel drivers, simply copy the orinoco-09b-patch.diff file to the /usr/src/linux/drivers/net directory and patch according to the directions on the Orinoco Monitor Mode Patch Page. You can double- check the version of the Orinoco drivers that shipped with your kernel by examining the first few lines of the orinoco.c file. Te Orinoco patches require either Solomon Peachy's patch to libpcap 0.7.1 (see his libpcap-0.7.1-prism.diff file, or his RPMs of that version of libpcap), or the current CVS version of libpcap, which includes his patch (download it from the "Current Tar files" section of the tcpdump.org Web site). If you apply his patches to libpcap 0.7.1 and rebuild and install libpcap, or if you build and install the current CVS version of libpcap, you would have to rebuild Ethereal from source, linking it with that new version of libpcap; an Ethereal binary package would not work. Ethereal binary packages might work if you install the libpcap-0.7.1-1prism.i386.rpm RPM, as it might install a libpcap shared library in place of the one on your system. On other platforms, capturing raw 802.11 packets on Orinoco cards is not currently supported. Other 802.11 interfaces: With other 802.11 interfaces, no platform allows Ethereal to capture raw 802.11 packets, as far as we know. If you know of other 802.11 interfaces that are supported (note that there are many "Prism II cards", so your card might be a Prism II card), please let us know, and include URLs for sites containing any necessary patches to add this support. On platforms that don't allow Ethereal to capture raw 802.11 packets, the 802.11 network will appear like an Ethernet to Ethereal. Q 5.30: How can I capture packets with CRC errors? A: Ethereal can capture only the packets that the packet capture library - libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on Windows - can capture, and libpcap/WinPcap can capture only the packets that the OS's raw packet capture mechanism (or the WinPcap driver, and the underlying OS networking code and network interface drivers, on Windows) will allow it to capture. Unless the OS can be configured to supply packets with errors such as invalid CRCs to the raw packet capture mechanism, Ethereal - and other programs that capture raw packets, such as tcpdump - cannot capture those packets. You will have to determine whether your OS can be so configured, configure it if possible, and make whatever changes to libpcap and the packet capture program you're using are necessary to support capturing those packets. Q 5.31: How can I capture entire frames, including the FCS? A: Ethereal can't capture any data that the packet capture library - libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on Windows - can capture, and libpcap/WinPcap can capture only the data that the OS's raw packet capture mechanism (or the WinPcap driver, and the underlying OS networking code and network interface drivers, on Windows) will allow it to capture. For any particular link-layer network type, unless the OS supplies the FCS of a frame as part of the frame, or can be configured to supply the FCS of a frame as part of the frame, Ethereal - and other programs that capture raw packets, such as tcpdump - cannot capture the FCS of a frame. You will have to determine whether your OS can be so configured, configure it if possible, and make whatever changes to libpcap and the packet capture program you're using are necessary to support capturing the FCS of a frame. Most if not all OSes probably do not support capturing the FCS of a frame on Ethernet, and probably do not support it on most other link-layer types. Q 5.32: Ethereal hangs after I stop a capture. A: The most likely reason for this is that Ethereal is trying to look up an IP address in the capture to convert it to a name (so that, for example, it can display the name in the source address or destination address columns), and that lookup process is taking a very long time. Ethereal calls a routine in the OS of the machine on which it's running to convert of IP addresses to the corresponding names. That routine probably does one or more of: * a search of a system file listing IP addresses and names; * a lookup using DNS; * on UNIX systems, a lookup using NIS; * on Windows systems, a NetBIOS-over-TCP query. If a DNS server that's used in an address lookup is not responding, the lookup will fail, but will only fail after a timeout while the system routine waits for a reply. In addition, on Windows systems, if the DNS lookup of the address fails, either because the server isn't responding or because there are no records in the DNS that could be used to map the address to a name, a NetBIOS-over-TCP query will be made. That query involves sending a message to the NetBIOS-over-TCP name service on that machine, asking for the name and other information about the machine. If the machine isn't running software that responds to those queries - for example, many non-Windows machines wouldn't be running that software - the lookup will only fail after a timeout. Those timeouts can cause the lookup to take a long time. If you disable network address-to-name translation - for example, by turning off the "Enable network name resolution" option in the "Name resolution" options in the dialog box you get by selecting "Preferences" from the "Edit" menu - the lookups of the address won't be done, which may speed up the process of reading the capture file after the capture is stopped. You can make that setting the default by using the "Save" button in that dialog box; note that this will save all your current preference settings. If Ethereal hangs when reading a capture even with network name resolution turned off, there might, for example, be a bug in one of Ethereal's dissectors for a protocol causing it to loop infinitely. The bug should be reported to the Ethereal developers' mailing list at ethereal-dev@ethereal.com. On UNIX-flavored OSes, please try to force Ethereal to dump core, by sending it a SIGABRT signal (usually signal 6) with the kill command, and then get a stack trace if you have a debugger installed. A stack trace can be obtained by using your debugger (gdb in this example), the Ethereal binary, and the resulting core file. Here's an example of how to use the gdb command backtrace to do so. $ gdb ethereal core (gdb) backtrace ..... prints the stack trace (gdb) quit $ The core dump file may be named "ethereal.core" rather than "core" on some platforms (e.g., BSD systems) Also, if at all possible, please send a copy of the capture file that caused the problem; when capturing packets, Ethereal normally writes captured packets to a temporary file, which will probably be in /tmp or /var/tmp on UNIX-flavored OSes and \TEMP on Windows, so the capture file will probably be there. It will have a name beginning with ether, with some mixture of letters and numbers after that. Please don't send a trace file greater than 1 MB when compressed. If the trace file contains sensitive information (e.g., passwords), then please do not send it. Q 5.33: How can I search for, or filter, packets that have a particular string anywhere in them? A: Currently, you can't. That's a feature that would be hard to implement in capture filters without changes to the capture filter code, which, on many platforms, is in the OS kernel and, on other platforms, is in the libpcap library. It would be easier to implement in display filters, but it hasn't been implemented yet. It would be best implemented as a display filter "string match" operator, which would let you check not only the entire packet for a string, but check portions of the packet for a string. It should probably not use a naive string matching mechanism, as there are mechanisms much faster than the naive one. Support can be found on the ethereal-users[AT]ethereal.com mailing list. For corrections/additions/suggestions for this page, please send email to: ethereal-web[AT]ethereal.com Last modified: Sun, May 25 2003.