[c-nsp] intra-chassis stacking

Seth Mattinen sethm at rollernet.us
Fri Mar 30 12:31:40 EST 2007

Joe Abley wrote:
> Hi all,
> I am puzzling over a cisco 2851 which has both a HWIC-D-9ESW 9-port  
> switch module and a NM-16ESW-1GIG 16+1 port switch module.
> The switch modules do not seem to be behaving as I would expect. ARPs  
> are succeeding and failing apparently at random, OSPF adjacencies are  
> not forming, and general layer-2 badness abounds.
> The small amounts of cisco docs available about this configuration  
> suggest that "intra-chassis stacking" must be configured, but details  
> on exactly what that means are a little light. The best indication I  
> have seen suggests that I need to insert a crossover cable between  
> the optional gigabit modules on each of the cards; however, it  
> doesn't seem like gigabit ports are an option on the 9-port HWIC, and  
> the gig port on the 16+1-port NM is already in use.
> I have no requirement for VLANs to span the two modules -- I can  
> easily keep all the ports on the 9-port HWIC in a single VLAN, and  
> not expect any ports in the 16+1-port NM to join those VLANs.
> Any suggestions as to whether this configuration can be made to work  
> in a sane way?

Forgot to include this:


Look for the sections on "Intrachassis Stacking" and "Configuring Stacking".


More information about the cisco-nsp mailing list