[c-nsp] Catalyst 6500 Module Virtual Port Limit

[Matt Buford]

"Brant I. Stevens" <branto at branto.com> wrote:
> %PM-SP-4-LIMITS: The number of vlan-port instances on module 1 exceeded 
> the
> recommended limit of 1800
> %PM-SP-STDBY-4-LIMITS: The number of vlan-port instances on module 1
> exceeded the recommended limit of 1800
>
> This can be handled by removal of the extraneous VLANs from trunks that
> don't need a given set of VLANs.
>
> I was wondering if there was any more detailed information available about
> the above...  I found some information about this from Networkers 2005 in
> the Datacenter Solutions Techtorial, but was looking for a bit more detail
> about this.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800951ac.shtml#resource_error

Scroll down slightly to the table for links to the STP limitations for a 
number of platforms.

The short answer is that there is a limit on how many spanning tree 
port-instances can exist on a single slot.  If you have lots of VLANs and 
need to trunk them to lots of ports, you probably should consider switching 
to MST.  Depending on your configuration, you might be able to work around 
the problem (at least for a while) by ensuring that connections carrying 
large numbers of VLANs are spread out and mixed with single(or low) VLAN 
ports on the same cards.

Personally, I tend to run into this a lot when I use 16 port gig cards (and 
have no problem with 8 port gig cards).  I'll probably be switching to MST 
(from RSTP+) someday soon because of this.