# Arp table



## nulkarp (Sep 30, 2009)

I wonder how much time arp table refresh?

I want to save records of Arp

For this, I need to know the time of renewal.

____________________________________________________
Sorry for my bad english.


----------



## dennylin93 (Sep 30, 2009)

I think net-mgmt/arpwatch is what you're looking for.


----------



## DutchDaemon (Sep 30, 2009)

arp(4)


```
MIB Variables
     The ARP protocol implements a number of configrable variables in
     net.link.ether.inet branch of the sysctl(3) MIB.

     max_age       How long an ARP entry is held in the cache until it needs
                   to be refreshed.
```


```
$ sysctl -n net.link.ether.inet.max_age
1200
```

I know of no direct way to query a specific arp entry for 'how old it is', and I gather that each arp entry lives at most 20 minutes (1200 seconds) before it needs to be refreshed. So running a cron job that saves records (arp -a) every ~20 minutes may work.


----------

