entry is reset to 0 without removing the entry from the hardware. Traffic to
the host continues to be forwarded in hardware without interruption. If the
entry is not being used to forward data packets, then the entry is deleted from
the ARP cache, unless the dynamic renew option is enabled. If the dynamic
renew option is enabled, the system sends an ARP request to renew the entry.
When an entry is not renewed, it is removed from the hardware and
subsequent data packets to the host trigger an ARP request. Traffic to the
host is lost until the router receives an ARP reply from the host. Gateway
entries, entries for a neighbor router, are always renewed. The dynamic renew
option only applies to host entries.
The disadvantage of enabling dynamic renew is that once an ARP cache entry
is created, that cache entry continues to take space in the ARP cache as long
as the neighbor continues to respond to ARP requests, even if no traffic is
being forwarded to the neighbor. In a network where the number of potential
neighbors is greater than the ARP cache capacity, enabling dynamic renew
could prevent some neighbors from communicating because the ARP cache is
console(config)#no arp dynamicrenew
Use the arp purge command in Privileged EXEC mode to cause the specified
IP address to be removed from the ARP cache. Only entries of type dynamic
or gateway are affected by this command.
ip-address — The IP address to be removed from ARP cache.
This command has no default configuration.