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I'm trying to poll the arp table from a backbone switch but i want to understand which records are up. I just want to know if there is a specific time for the switch to keep a record on the arp table even if it doesn't get any traffic from an IP address.

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    Default arp timeout on Cisco switches or most routers are 4 hours. On Cisco Nexus default arp timeout is 1500 seconds.
    – user36472
    Mar 25 '19 at 12:17
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    Remember entries only get added to the ARP table if there was IP to ether address resolution. As switches very rarely do this, ARP tables are often pretty sparse. MAC forwarding tables, on the other hand, are for the switch to do its primary job: efficient frame forwarding. You might be better off looking at that.
    – jonathanjo
    Mar 25 '19 at 12:23
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    Are you asking about the MAC address table (which contains the list of MAC addresses seen on the switches ports) or the ARP cache (which map IP addresses to MAC addresses)? Those are two totally separate things.
    – JFL
    Mar 25 '19 at 12:25
  • I'm talking about the arp cache.
    – user19215
    Mar 25 '19 at 13:29
  • We cannot answer your question without the specific switch model. Layer-2 switches do not use ARP, they have MAC address tables. The router module of a layer-3 switch will have an ARP table, too.
    – Ron Maupin
    Mar 25 '19 at 13:31
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I assume you are in fact asking about the switch MAC address table (the real name according to 802.1D-2004 is actually filtering database but it is never used in practice).

As you can infer from @Cown comment, this is dependent of the switch model and can vary from minutes to hours. It may also be configurable.
You will have to check the documentation and the current configuration of your switch to be able to answer your question.

Also, each entry is (by the very purpose of the table) associated with a port, and on most switches the entry will be immediately removed from the table if the port goes down.

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