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difference betn L3 switch n router

Dear All,

what are the main differences between L3 switch and router? can we replace a router with L3 switch as its router module supports routing ????? in ospf network can L3 switch elected as DR r BDR ???? can anybody clear me Pls

Thanks in advance




Re: difference betn L3 switch n router

Hi Nataraj,

Layer 3 routing is the concept used mainly for the routers which routes the packet between diff n/w. The layer 3 switching is used for the switches whihc are capable of doing both the routing and switching on the same box. i.e they have for L2/l3 capability.

The fundamental difference between a router and a Layer 3 switch is that Layer 3 switches have optimized hardware to pass data as fast as Layer 2 switches, yet they make decisions on how to transmit traffic at Layer 3, just like a router. Within the LAN environment, a Layer 3 switch is usually faster than a router because it is built on switching hardware. In fact, many of Cisco's Layer 3 switches are actually routers that operate faster because they are built on "switching" hardware with customized chips inside the box.

Yes, you can replace a router with a L3 switch. You cannot terminate your WAN connections on L-3 switches like ISDN BRI/PRI. ASYNC connections etc... Though on some of the switches you cna terminate T1/E1 like 4500 and 6500's.

yes OSPF DR and BDR is also elected in a L3 switch. DR and BDR is not a routers property its a interface or the link type property. The router with the highest Router ID will become the DR.


-amit singh


Re: difference betn L3 switch n router

You can find information about the functions of a L3 switch in comparison to a L2 switch and a router by clicking on the following link:

I do not know the answer to your question regarding L3 switches and ospf, but maybe someone else can help you out with that!


Michael Freijser

Re: difference betn L3 switch n router

Hi Natraj,

The major difference between L3 switch and router is regarding performance. Routing on router is software base which is cpu intensive and routing done on layer 3 switches can be done on hardware which is less cpu intensive and gives you better performance.

Yes ofcource if you use l3 switch for ospf routing protocol it can be detected as DR and BDR depending upron your ospf configuration.

Also DR and BDR depends on whether you have broadcast media or not if you have let it be a router or layer 3 switch it does not matter and it will elect DR and BDR.

Problem comes when you want to terminate you wan lines like frame relay and lease lines. Not all layer 3 switches support that. Big daddy like cat6k still supports wan modules on which you can even terminate your wan lines.

So the major difference lies on performance.