ARP Timeout in Cisco IOS

If you’re managing Cisco IOS routers, you might want to adjust the settings for ARP cache timeout. The default value is 4 hours which can be a long time to wait if you are changing out hardware and using the same IP with a new mac address. This setting is managed in the interface configuration mode separately for each layer three (IP) interface. Read the following Cisco document for help with this feature – Configuring Address Resolution Protocol: Expiration Time for … ARP. Here are some sample commands.

  • interface gig0/0
    • arp timeout 300
  • show interface gig0/0 | include ARP Time

UPDATE 27 Jan 2016 – Adding equivalent ARP timeout information for Cisco ASA firewall products. The default ARP timeout on Cisco ASA is the same 14400 seconds (4 hours). This can be changed as a global setting on the ASA using commands like the following (example using 300 seconds = 5 minutes):

  • arp timeout 300
  • show run arp timeout

See my related post Cisco ASA ARP Behavior for discussion of some other ARP settings on the ASA.

About notesbytom

Keeping technology notes on to free up my mind to solve new problems rather than figuring out the same ones repeatedly :-).
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