Re: CAM table not updating after STP TCN

Ramesh,
STP TCN would force a CAM fast age, but has no way to force an update.
You need traffic to do that. In fact, traffic will update/refresh the
CAM all the time (w/o TCN).

ARP is not usually related to TCN, although some switches have an
"optimization" that clears the switch ARP table in case of TCN, which
helps when the switch is working at L3 (i.e. it's the DG for hosts).

What kind of switches are you using ? Can you describe the topology so
we can follow what is surprising you ?

-Carlos

ramesh Kumar @ 14/01/2013 07:50 -0300 dixit:
> I have 2 switches connected back to back on port-channel 1. As per my
> understanding after any STP change, I should see CAM table update and shortly
> after that ARP table update. I see the ARP being refreshed but it looks like
> the CAM table on SW2 didnt update.
>
>
> SW1# sh ip arp | i 34a8.4eb6.0aa2
> 172.20.210.38 00:01:10 34a8.4eb6.0aa2 Vlan2010
>
>
> SW1# sh mac add
> dy | i 34a8.4eb6.0aa2
> * 2010 34a8.4eb6.0aa2 dynamic 0 F
> F Eth1/9---> aging time 0 shows that we are getting traffic hitting this
> entry continuously. Right?
>
>
> SW2# sh ip arp | i 34a8.4eb6.0aa2
> 172.20.210.38
> 00:01:14 34a8.4eb6.0aa2 Vlan2010
>
>
> SW2# sh mac add dy | i
> 34a8.4eb6.0aa2
> * 2010 34a8.4eb6.0aa2 dynamic 120 F F
> Po1----> it seems the CAM timer didn't reset after TCN but the ARP refreshed
> The link between the switches are configured like this and these switches are
> running HSRP for all the vlans with SW1 being STP root and HSRP primary for
> all the vlans
>
>
> interface port-channel1
> switchport
> switchport mode trunk
>
> switchport trunk allowed vlan 2,650,660,720,730,790,1920,1930
> switchport
> trunk allowed vlan add 1640,1960,1910,1930,1490,2000,2010
> spanning-tree
> link-type point-to-point
> mtu 9216
> load-interval counter 1 60
>
>
> For arp
> there is a command "show ip arp internal event-history" which can show if the
> arp was refreshed due to a TCN or not. which command can help in checking if
> mac table was refreshed due to TCN or not apart from show mac address table?
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net