[c-nsp] Vlans and catalyst 2950

[Adrian Pirciu]

Hello

Alban Dani wrote:
> Hello Matthew,
> 
> I also am having a very wierd issue with vlans and 2950-s.
> 
> We are running pst+.
> We have a 6509 in the core and everytime we try to get a new vlan
> passed through a chain  of switches( all connected via dot1q trunks) 
> that has a 2950 in it, it does not work. The only workaround we found
> so far is to go to a port on the given 2950 , set the port on the
> requried vlan and connect a machine to it and through some traffic.
> That makes the 2950 aware of  that vlan.

a 2950 will not pass traffic for the vlans not defined in its table. 
When you put a port in a vlan, it automatically adds this vlan to the 
config (sh vlan) and it starts forwarding traffic for that vlan which 
explains the behaviour you describe.

You can use VTP if you want to have a consistent vlan database accross 
you network. Be careful though (there are some bat things that can 
happen, read the documentation from www.cisco.com and they are 
described).


> 
> If this was not enough, if the vlan in question does not see traffic
> for a couple of days the 2950 totally forgets about it.

I am not aware of anything resembling this behaviour. Anybody ? Does 
the vlan apper on "sh vlan" when this happens ?

> 
> I am wondering if you ever found a solution to your problem and if so
> what was it?
> 
> I have upgraded to the latest IOS but it did not help.

i'm pretty sure it is not an IOS/switch related problem.

> 
> thanks,
> 
> Alban
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adixor