DOCUMENT:Q103295  14-SEP-1993  [W_NT]
TITLE   :Using ARP in Windows NT Requires IP Activity or PING
PRODUCT :Windows NT
PROD/VER:3.10
OPER/SYS:WINDOWS
KEYWORDS:

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The information in this article applies to:

 - Microsoft Windows NT operating system, version 3.1
 - Microsoft Windows NT Advanced Server, version 3.1
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SUMMARY
=======

The Address Resolution Protocol (ARP) is a utility program that you
can run at the Windows NT command prompt to add, delete, or view the
entries in the ARP table for IP and physical addresses. However, you
may need to run the PING utility or any IP activity before you can
execute the ARP.

MORE INFORMATION
================

The ARP, included as a part of the TCP/IP in Windows NT, is used to
obtain the physical address corresponding to an IP address. ARP
defines a broadcast-based method for dynamically translating between
IP addresses and physical addresses.

Before you can send data between two network workstations, the
physical addresses must be known. ARP gives you this capability: with
ARP you do not need to know physical addresses and manually add them
to a table.

System administrators can use the ARP utility program to construct and
maintain a table of physical addresses corresponding to IP addresses.
The address table is kept in the ARP cache. The physical address
information is stored temporarily (9 minutes). However, the physical
address of the host is always known and not shown when the ARP table
is viewed. When this address is added manually to the table, it is
shown as permanent.

To create and view the address table, do the following:

1. Ping a known IP address at the command prompt.

2. View the ARP table by running the following command:

      ARP -G

NOTE: The ARP entries are only added to the ARP cache when an ARP is
done for that address. When PING is run and the ARP entry did not
exist in the ARP cache, an ARP packet will be generated and upon
response from the machine claiming the IP address, the ARP entry will
be added to the ARP cache. You can use use PING or any IP-based
activity. These entries will be temporary entries. You can also
manually add ARP entries to the ARP cache by using ARP -A. If you use
ARP -A, an ARP request will not be generated when communicating with a
particular machine.

Additional reference words: 3.10
KBCategory:
KBSubCategary: tpip

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