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.

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About notesbytom

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