ArpCacheSize Defaults to 62 Entries

• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

A Windows NT server may not be able to maintain reliable connections to a large number of active TCP/IP clients.

CAUSE

The default ArpCacheSize is set to 62 entries. The ArpCache maintains a mapping between IP and machine addresses, so the size should be adjusted to accommodate the number of active clients. Otherwise the oldest entries will be purged and then address resolution protocol (ARP) will be used to re- obtain the mappings when they're needed.

RESOLUTION

NOTE: This resolution only applies to Windows NT version 3.1. In Windows NT 3.5 and 3.51, the ArpCacheSize is dynamic and the registry parameter does not exist anymore.

You can adjust the ArpCacheSize in Windows NT 3.1 by using the following procedure:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

1. Start Registry Editor.

2. Select the HKEY_LOCAL_MACHINE on Local Machine window.

3. Go to the SYSTEM\CurrentControlSet\Services\tcpip\parameters key.

4. Create a new value of type REG_DWORD named ArpCacheSize.

5. Set it for the highest number of clients that is likely to be active at one time.