router with HWIC-9ESW for trunk distribution

Unanswered Question
Apr 3rd, 2009


I'd like to confirm that this will work as expected. We are expanding our network. We plan to have a pair of 3825 routers with HWIC-9ESW switch cards installed, to use for distribution of traffic into actual 29xx and 35xx switches. The 9ESW has a VLAN database that restricts it to only recognizing 15 VLANs.

Our understanding is that this will not affect the distribution of VLAN traffic through the HWIC when ports are used as trunk ports -- only when used HWIC ports are for access. In other words, we could have 50 subnets and VLANs defined in the 3825 routers, connect the routers to downstream switches via 802.1q trunk ports on the HWIC-9ESW, and there would be no issue with those tagged packets transiting the HWIC intact and being distributed to the switched network. We believe this to be the case, but confirmation from real experience would be useful. Thanks.


I have this problem too.
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Giuseppe Larosa Mon, 04/06/2009 - 05:14

Hello Larry,

use a L3 switch like C3560 if possible.

A limitation on the size of the vlan database should mean at least that no more then 15 SVI can be up/up at the same time.

You might be able to pass vlan tags but not to provide L3 services to 50 vlans this is almost sure.

the SVI needs a live L2 broadcast domain to be up/up on switches but if only 15 L2 vlan objects can exist how can the other SVI interfaces work ?

Hope to help



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