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Author Topic: avaya 5632FD (and other routing switches) arp table overflow  (Read 3802 times)

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Offline Marianne

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hello,
i am wondering if i understood this correct:  about  ip arp timeout /lifetime on avaya routing switch:
is it true that if this is for example 120minutes, so 2 hours, that the entry is refreshed (if there is enough space/memory) after 120 minutes?
it is not regularly refreshed/reset (during that 2 hours) when traffic of a device is passing through the routing switch?

if that is the case:
so if the arp table if full and the lifetime of my entry reaches its 2 hours (so needs a refresh) and another device needs an entry at the same time, my session might be 'killed' because my device's ip-mac couple cannot be found?

PS we already upgraded to a version with a greater arp table entries capacity

Marianne


Offline TankII

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Re: avaya 5632FD (and other routing switches) arp table overflow
« Reply #1 on: July 17, 2013, 03:28:48 PM »
2 hours?  That's excessive.
Your bridge timer should be 21601 per the documentation.

That's in seconds, not minutes.  The default is 300 seconds, or 5 minutes.

TankII

Offline Michael McNamara

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    • michaelfmcnamara
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Re: avaya 5632FD (and other routing switches) arp table overflow
« Reply #2 on: July 18, 2013, 03:13:45 PM »
Hi Marianne and welcome to the forums!

The default ARP TTL on the Avaya products is usually 6 hours while the default MAC/FDB TTL is usually 5 minutes. This will vary depending on the switch model although it's consistent between software releases.

The answer to your question will vary depending on the model of the switch we're talking about.

In the case of the ERS 8600, the switch will automatically re-ARP for the information once the ARP entry expires. If the MAC/FDB entry expires it will automatically expire any associated ARP entries that's why Avaya recommends the MAC/FDB timer be set to 21601 (60 seconds * 60 minutes * 6 hours + 1 second). If you keep the standard MAC/FDB timer you'll notice an ARP storm in large networks where the ERS 8600 will re-ARP every 5 minutes (300 seconds) not because the ARP TTL is expiring but because the MAC/FDB TTL is expiring.

As to what happens when/if the ARP or MAC/FDB were to actually fill... I'm not 100% sure myself so I won't comment but I would suggest it should NEVER fill up.

Cheers!

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