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New Member

layer 3 switching

Can anyone tell me how I would go about using a L3 switch as a router, do I just need to anable ip routing and then assign an ip to one of the interfaces, using the no switchport command ?

thanks

Carl

8 REPLIES
Cisco Employee

Re: layer 3 switching

Hi Carl, that is correct, and operation is just as you would see on a pure router.

Additionally, a layer 3 switch allows you to route to and from multiple vlans without having to use a separate physical interface for each subnet/vlan. See the following document for an explanation of InterVLAN routing and how to configure it.

http://www.cisco.com/warp/customer/473/189.html

Bronze

Re: layer 3 switching

It all depends on the switch you have. Some switch may require different IOS, for others it may be configuration. Please specify the switch model and IOS version.

New Member

Re: layer 3 switching

it will be a 3550 switch, Does it use the ip address of the port interface or ip address of a vlan interface for the ip represnting the router, I want to use it as a normal router, not vlan routing .

thanks

Re: layer 3 switching

Hi

In 3550 you can configure the ports with ip address but before that u need to make them as L3 interface which is L2 by default.

you need to key in no switchport under the interface mode config to make it as L3 once ur thru with this then you can configure the ip address on the interface.

regds

New Member

Re: layer 3 switching

Depending on whether or not you have the SMI or EMI version of the IOS will determine which routing protocols are available to you. IF you want to use OSPF or EIGRP, then you will need the EMI IOS. If you are only doing static or RIP, I believe you will only need the SMI version.

New Member

Re: layer 3 switching

So if I put an ip on one of the interfaces, dp all the other ports on the switch just act like normal ?

Bronze

Re: layer 3 switching

That correct if you do a no switchport command on one of the interface and assign it an ip address, all other ports will act normally.

You can verify that the port you've configured is in fact layer 3 by doing "show int fastethernet x/yy switchport". It should say switchport is disabled.

New Member

Re: layer 3 switching

yes you are right, just execute no switchport command and then give the IP aaddress, and for InterVLAN routing you can just configure IP addresses in the VLAN interface and enable IP routing in the global configuration mode.

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