Arp Purge - Dell PowerConnect 8024 Cli Reference Manual

no arp dynamicrenew
Default Configuration
The default state is enabled.
Command Mode
Global Configuration mode
User Guidelines
When an ARP entry reaches its maximum age, the system must decide whether to retain or
delete the entry. If the entry has recently been used to forward data packets, the system will
renew the entry by sending an ARP request to the neighbor. If the neighbor responds, the age of
the ARP cache 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
full.
Example
console#configure
console(config)#arp dynamicrenew
console(config)#no arp dynamicrenew

arp purge

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.
Syntax
ip-address
arp purge
553
ARP Commands