When is a layer 3 switch more appropriate than a router in a branch office?

Question

It seems that as time passes, vendors have added almost all the features of a router to a layer 3 switch.

For branch office deployments, how do other people who design networks choose between deploying a router + a layer 2 switch vs deploying just a layer 3 switch?

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score 5 · Answer 1 · answered Jul 05 '14 at 08:34

Layer 3 switch doesn't provide the typical edge features used on a router:

NAT/PAT (along with IPv4->IPv6 transition technologies)
Stateful Firewall
HQoS for multiple classes of traffic at a rate Ethernet is shaped/policed on the ISP side (usually you'll get subrate service, not full bandwidth of the Ethernet port connected to the device)

That said, for the inter-vlan routing in most of the scenarios the L3 switch will perform better and cause less problems, as small/edge routers are still using CPU to route the traffic and performance may be not ideal.

So propably you'll want L3 switch and edge router.

score 4 · Answer 2 · answered Jul 05 '14 at 09:49

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The distinction between "Layer3 Switch" and "Router" is muddy and not defined. Vendors use whatever term they think is best for PR (sometimes switching between both terms). L3 Switch and router can be substituted almost any time. You must look at the feature list to see if the device has all the features you need for your branch office.

answered Jul 05 '14 at 09:49

Sebastian Wiesinger

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Switch (L3 or not) and router have different technical definitions. Just because Company X's PR group tries to change that with words doesn't make it true. – cpt_fink Jul 09 '14 at 05:32
So point me to those definitions. In my experience there are none that are valid between vendors. – Sebastian Wiesinger Jul 09 '14 at 11:27

score 3 · Answer 3 · answered Jul 08 '14 at 00:54

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I use routers for my remote office ethernets because since I do not buy line rate 'CIR' I need to traffic shape. Switches don't do that. Router QoS is also easier to deal with because switch QoS has lots of hardware dependencies.

answered Jul 08 '14 at 00:54

fredpbaker

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Modest correction: [some switches can do traffic shaping](http://www.cisco.com/c/en/us/td/docs/routers/7600/install_config/ES40_config_guide/es40_sw_config/es40_chap7.html#wp1346884) – Mike Pennington Jul 08 '14 at 00:58

When is a layer 3 switch more appropriate than a router in a branch office?

3 Answers3