Branch routing - Cisco ISR or L3 switching

I'm looking for design/scale recommendations for intra-site routing  when provisioning a branch office. Specifics for this example:

- multiple VLANs/subnets at each branch (voice, video & data)
- Cisco ISR router (voice gateway) at the edge, providing WAN routing and PSTN termination outside of the branch
- any number of switch ports internally (which leads to my question)

I know the WAN router is capable of providing all routing for the branch subnets, but at what point would proper design recommend off-loading this burden to a more capable device (an internal L3 switch), rather than passing everything to a box that was built to provide services, moreso than packet-switching speed, especially for sites provisioned with Gigabit Ethernet endpoints?

I haven't yet found a document w/ specifics around where the edge router might not be the recommended router for the branch, and when a L3 switching front-end would be the better choice.

Thank you, and reference links/docs are always appreciated!
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Not sure that I understood you well but...

You would like to offload some of the traffic in your branches to a more capable L3 switch.

Ok, then I don't think you have much choice here because full gigabit L3 is very expensive and  I don't suppose that you want 10000 USD more budget for every branch office out there.

So, monitor the router with snmp and change accordingly.

Here are my proposition, if you really need it:
24 Gigabit ports + uplink and everything's there you'll ever need in a branch office.
L3 routing but no ospf on basic ios. It's about 1500USD.

cfan73Author Commented:
Thanks for the feedback - I need to provide some additional info...

We're already deploying a full gigabit switching solution in the branch (with gig IP phones and piggy-backed workstations) - specifically, Cisco 2960-S PoE switches. This particular customer will require 100+ ports, so we're in 3x switch land already.  The 2960s are Layer 2-only, of course, so this would place all of the intra-site routing burden on the border/edge ISR/voice gateway, which isn't built for line rate routing.  I could "upgrade" one of the 2960s to a 3560-X (24-port PoE) for about an extra $2K to the customer, w/ IP Base licensing.

So, let's forget $$ for this, and just focus on performance/scalability/bottlenecks.  I'm looking for recommendations/design guidelines for when it would make sense (again, performance-wise) to offload the routing burden from the ISR.  I can present/argue the benefits to the customer, $-wise, when it comes to that point.  :)

Thanks again.
OK, thanks for clarification.

I strongly recommend powerful 3560X series. More than enough. 3750X is about stacking I don't see that you need that, although...  You could check this if you want to go 10G path WS-C2960S-48FPD-L.


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cfan73Author Commented:
Additional input, folks?  Again, looking for guidelines as to when it would be recommended to NOT use the edge router for internal inter-VLAN routing.

cfan73Author Commented:
Was hoping for additional info/guidance on when do decide between a router and a L3 switch for these types of deployments. I understand the recommendations, but I don't believe my real question was really addressed.
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