null ARP table on a C5 stack

[Omar_Valente]

I have a stack composed of 2 C5 series with F/W Fw:06.71.03.0025

It's some day that I'm experiencing networks problems (hosts becoming unreachable and getting back online after a random time)

The only strange thing that I've noticed is that the "show arp" command returns null adrresses

C5(su)->show arp
LINK LEVEL ARP TABLE
IP Address Phys Address Flags Interface
---------------------------------------------------------
10.104.2.14 00-00-00-00-00-00 host
10.101.2.226 00-00-00-00-00-00 host
10.101.2.241 00-00-00-00-00-00 host
10.101.3.92 00-00-00-00-00-00 host
10.101.50.5 00-00-00-00-00-00 host
10.103.2.134 00-00-00-00-00-00 host
10.103.10.11 00-00-00-00-00-00 host
---------------------------------------------------------

Any idea on what caused/how to fix this ?

Thank you

Omar Valente

[Omar_Valente]

Robert: I had to set a a very short age time for the mac table.... I had to set it to like 15 seconds to prevent this from happeining. This caused an higher CPU consumption but that was not an issue for me.

Hope it Helps

Omar Valente

[Robert_J]

Hello, it seems that we have similary problems. Could you solved your problem ?

We although have a stacked C5 Coreswitch with Routing functions, Vers Fw:06.71.05.0008

We see in some vlans the same issue, some hosts are not reachable for an undefined time from other vlans. In the router arp, the host are still registerd, int the switch mac table they are missing. After a ping from the router the the hosts , they are reachable again. from all other vlans.
It seems, that the switch do not forward arp request or renew his own mac address table.

Next Step will be a SW upgrade

[Daniel_Fengler]

If it is a router then go in "router"-Modus:

C5(su)->router

C5(su)->router>enable

C5(su)->router#Show ip arp

[Omar_Valente]

For what I have been understanding that's normal when the switch is doing routing too

Omar Valente