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tomislav91
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Posts: 97
Joined: Fri May 26, 2017 12:47 pm

arp table flash?

Tue Jun 30, 2020 11:13 am

Hello guys, i have several ip which i put static IP, but in arp table there are entries for that mac for that STATIC and DYNAMIC ip.
I have restarted device, but result is the same.

How much time i must wait for arp table to be updated
 
sindy
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Joined: Mon Dec 04, 2017 9:19 pm

Re: arp table flash?

Tue Jun 30, 2020 11:43 am

A row in the ARP table (IP to MAC translation) of a router is only automatically created when a packet needs to be delivered to a host whose IP is in a connected subnet. So until you try to ping that IP, or some packet for it comes from outside, the ARP record will never appear automatically. This is a difference as compared to MAC forwarding table of a switch/bridge, where the mapping between a MAC address and an interface is created whenever a frame from that MAC address arrives via that interface.

In both tables, dynamically created rows have a lifetime - if there is no update before the lifetime expires, the row is automatically removed.

To both tables, you can add a row manually; such rows are stored into the configuration so they survive a reboot.

You can configure the DHCP server to create an ARP record once it leases out the address to a client, and remove it when the lease expires. Nothing similar exists for MAC table for switches/bridges.
Instead of writing novels, post /export hide-sensitive. Use find&replace in your favourite text editor to systematically replace all occurrences of each public IP address potentially identifying you by a distinctive pattern such as my.public.ip.1.

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