Setting up DHCP and WINS servers
You can use Corel LINUX to set up DHCP (Dynamic Host Configuration Protocol) and WINS (Windows Internet Naming Service) servers to handle many of the communication requirements for your network. A DHCP server dynamically allocates IP addresses to network clients. A WINS server provides dynamic address resolution for Windows clients.
To communicate over a network, computers must identify other computers on the network. One of the most common ways to identify computers on a network or the Internet, is using an IP address. The allocation and management of IP addresses is one of the most important network administration tasks. IP addresses must be unique within a network. They must also be properly configured on the client's computer so that other network users can contact it.
Using DHCP, the network administrator specifies a range of IP addresses, which are dynamically allocated to network clients by the server.
Another way to identify computers is using a NetBIOS address. A NetBIOS address is a numerical address similar to an IP address. While IP addresses are used across all types of computer platforms, NetBIOS addresses are typically used by computers in Windows networks. Computers can have both an IP address and a NetBIOS address.
WINS servers use NetBIOS addresses to provide dynamic address resolution for Windows clients. WINS can resolve name requests in a network with a DHCP server because it uses NetBIOS addresses to identify computers rather than IP addresses, which change frequently when using DHCP.
This documentation is an introduction to how to set up DHCP and WINS servers using Corel LINUX. For more information about Linux and servers, visit the Resources site on the Corel LINUX web site. The Corel LINUX web site is located at http://linux.corel.com.
DHCP
The DHCP server responds to requests from clients for IP addresses. When clients request an IP address, the DHCP server allocates an IP address to the client for a specific length of time, referred to as a lease. When the lease expires, the IP address becomes available for use by other network clients.
A DHCP server is useful for a number of reasons. Dynamically allocating IP addresses using a DHCP server means that clients do not configure IP addresses on their computers. IP address configuration tasks are performed only by the server, which eliminates client configuration errors.
A DHCP server can save network administration time if a change is made to the configuration of IP addresses in the network. In such a situation only the DHCP server needs to be reconfigured, not each individual computer in the network.
A DHCP server also helps to conserve IP addresses. This is useful when the computers in a network outnumber the IP addresses that the network has available to use. Because the DHCP server allocates IP addresses only to computers that request an address, all unused IP addresses are available for use by other computers in the network.
When a DHCP client is started for the first time, it sends out a broadcast request to the network over port 67. The DHCP server daemon, dhcpd, listens to port 67 for incoming client messages. When the server receives the broadcast request, it checks to see if it has an available IP addresses. If the server has an available IP address, it sends the client a message offering the address. When the client receives the offer, the client responds to the server with an instruction to send the IP address. The server then sends the address to the client with the details of the lease. After 50 percent of the lease time expires, the client begins to send requests to the DHCP server to renew the lease. If the lease expires, the client repeats the request process until the client is allocated a new IP address by the server.
The DHCP server consists of the dhcpd server daemon, the dhcpd.conf configuration file, and the dhcpd.leases file. The dhcpd.conf file contains the configuration information used by the dhcpd daemon to allocate IP addresses. The range of IP addresses that the server can allocate, the subnet and netmask of the network, and the length of the leases allocated by the server, are specified in the dhcpd.conf file. The dhcpd.lease file keeps a record of the IP address leases.
You can install the DHCP server components when you install Corel LINUX with the server option. If you install Corel LINUX with the Standard Desktop, you can use Corel® Update to add the DHCP server. For information about installing Corel LINUX, see "Installing Corel LINUX" in the Corel LINUX User Guide. For information about installing the DHCP server using Corel Update, see "Installing servers on Corel LINUX."
The lease length depends on the network requirements. For example, if there are more computers on the network than IP addresses, you might specify a shorter lease length so that IP addresses are available on a regular basis.
For information about setting up a DHCP server, see "Setting up DHCP servers."
WINS
A WINS server records and stores the NetBIOS addresses and hostnames of computers on the network, and provides this information to network clients. WINS servers reduce network traffic because clients request information from the server instead of broadcasting requests to all computers on the network.
A hostname is a name, such as "corelpc", that is assigned to a computer. Hostnames are easy to remember and are used more frequently than IP or NetBIOS addresses for common user tasks. For example, when you want to find a computer on the network using the Find utility, you search using the hostname. A WINS server matches hostnames to the NetBIOS addresses computers use to communicate. A Domain Name Service (DNS) server is another naming server, but it matches hostnames to IP addresses, rather than to NetBIOS addresses.
A WINS server is useful in a network with a DHCP server because WINS identifies computers using NetBIOS addresses. With a DHCP server, the IP addresses in the network change frequently and are not a reliable indicator of a computer's identity.
When a network client first logs on to the network, the client requests that the WINS server register its hostname, "corelpc," for example. If no other client has registered that hostname, the WINS server adds "corelpc," and the NetBIOS address that corresponds to the hostname, to its configuration file. When another Windows client wants to communicate with "corelpc," to access a shared directory for example, the client sends a request to the WINS server asking for the NetBIOS address of "corelpc." When the WINS server responds with the address, the client can make contact with "corelpc" over the network.
The WINS server that comes with Corel LINUX is part of the Samba server package, which also includes file and print sharing services and a PDC service. The Samba server package includes the two Samba server daemons, smbd and nmbd, and the Samba configuration file, smb.conf.
The Samba server is installed when you install Corel LINUX with the server option. You can also install the Samba server using Corel® Update. For information about installing Corel LINUX, see "Installing Corel LINUX" in the Corel LINUX User Guide. For information about installing Samba using Corel Update, see "Installing servers on Corel LINUX."
You can set up the Samba WINS server using the Samba Server Wizard. For information about how to set up a WINS server, see "Setting up WINS servers using the Samba Server Wizard" on page . For information about Samba, see "Setting up file and print servers."