[c-nsp] What happens during the "shutdown" and "no shutdown" to a 1000BASE-LX10 port

[Terence Scott]

Hi Martin,

Can't say for sure but what may have happened is that Gi0/24 on the 
2960G may have entered the err-disable state for some reason (one 
possibility is a temporary bridging loop - check your spanning tree 
settings). When a port is in err-disable state the output of the "show 
interfaces" command shows no deviation from when the port is operating 
normally so you need to do a "show interfaces status". Once a port 
enters the err-disable state the only way to restore normal operation is 
to issue the "shutdown" and "no shutdown" commands. You can use the 
"errdisable recovery interval" command to set a timer for a port to 
automatically come out of err-disable state, however this should be used 
with caution (there is usually a good reason for a port to enter the 
err-disable state so it isn't a good idea to re-enable it before the 
root cause is resolved).

Cheers,

Terence

-------- Original Message --------
*Subject: *[c-nsp] What happens during the "shutdown" and "no shutdown" 
to a 1000BASE-LX10 port
*From: *Martin T <m4rtntns at gmail.com>
*To: *cisco-nsp at puck.nether.net
*Date: *10/08/2011 11:56 PM
> I have a following connection:
>
> WS-C2960G-24TC-L[Gi0/24]<->  [1/8]Brocade_switch
>
>
> ..and today after few flaps between the two switches because of the
> cabling works, the ports in both switches came up:
>
> Gi0/24    ->  Brocade  connected    trunk      a-full a-1000 1000BaseLX SFP
>
> ..and according to "show interfaces Gi0/24 switchport", the I Gi0/24
> seemed to be working fine. However, I could not see any MAC addresses
> on VLAN's allowed to this trunk port. Finally I did "shutdown" and "no
> shutdown" to the Gi0/24 port and all of the sudden, I saw MAC
> addresses on VLAN's. There were no differences in "show int status" or
> "show int Gi0/24" before and after the "shutdown" and "no shutdown". I
> don't manage the Brocade switch. SFP in Gi0/24 is made by Finisar.
> There is nothing interesting in the log of the Cisco switch.
>
> I'm just curious, what might happened and how did the "shutdown"/"no
> shutdown" improve the situation? Or is it impossible to analyse such
> problems(afterwards)?
>
>
> regards,
> martin
>