ARP Cache Management with Windows NT 3.5 and 3.51

The information in this article applies to:

• Microsoft Windows NT Workstation versions 3.5 and 3.51
• Microsoft Windows NT Server versions 3.5 and 3.51

SUMMARY

The Address Resolution Protocol (ARP) allows a host to find the physical medium access control (MAC) address of a destination host on the same physical network given the destination IP address. To make ARP efficient, each computer caches IP-to-MAC address mappings to eliminate repetitive ARP broadcast requests. This article describes the feature that eliminates unused ARP cache entries for higher cache efficiency.

MORE INFORMATION

Windows NT 3.5 and 3.51 cache management allows the ARP cache size to change automatically by flushing it from unused entries. The process is used to control ARP resources. Entries are aged out of the ARP cache if they are not used for two minutes. Entries that are being used within the first two minutes get aged out of the ARP cache after 10 minutes by default. Static entries (entries entered manually using the ARP -S command) are not aged out and remain in the ARP cache until the system is rebooted or manually deleted (using the ARP -D command).

Currently, Windows NT 3.5 and 3.51 ARP cache management implementation does not allow any changes to the ARP cache defaults. The initial 2 minute lifetime and the 10 minute ArpCacheLife are not configurable.