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Prefered method for creating routable connection between 2 switches

Just wondered which is the prefered method for connecting two switches so there is a routable connection between each switch.

Would it be by a configuring a layer 3 port on each switch and assigning an ip address to each port.

OR

Using a layer 2 trunk between each switch and create an SVI on each switch in the same network?

Many Thanks

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Accepted Solutions

Re: Prefered method for creating routable connection between 2 s

If you don't need to span VLAN's between the two switches (or beyond?) then the preferred method is to use routed interfaces (no switchport) and place the IP addresses directly on the physical interfaces. The reason for this is it removes the layer-2 issues of STP - Interfaces don't have to go through Listening, Learning & Forwarding states and immediately go Up when connected. There isn't the possiblily of someone screwing around with VLANs and/or other trunks on the switch and causing an STP reconvergence on the link etc.

If you must use SVI's and a trunk then make sure the bandwidth statements of the routed interfaces are correct as they will default to either 100Mbps or 1Gbps depending on which switch or router you are working on. With physical interfaces the bandwidth will be correct.

Have a read of the Layer-3 access design guide on the SRND site

http://www.cisco.com/go/srnd

HTH

Andy

4 REPLIES

Re: Prefered method for creating routable connection between 2 s

Depending on the type of switch that you have. "Routable" indicates that you'll be using a L3 in which case you'll be routing your traffic between SVIs (inside of the switch) and next hops (outside of the switch). In either case, to interconnect switches will use trunks which is L2. The SVI on a L2 switch is used for management (telnet) purposes only, and you won't be able to route to or through it without a L3 device (like a router).

HTH,

John

HTH, John *** Please rate all useful posts ***
Gold

Re: Prefered method for creating routable connection between 2 s

I think both would work.

if the ppl who are to use it or around it are not so experienced I would actually go with the layer 3 port and a cable between them. It is so much easier to show them and to have them understand that type of solution.

However the best way I would think would be the trunked and svi solution. more scalable when it comes to bandwith and such.

Re: Prefered method for creating routable connection between 2 s

If you don't need to span VLAN's between the two switches (or beyond?) then the preferred method is to use routed interfaces (no switchport) and place the IP addresses directly on the physical interfaces. The reason for this is it removes the layer-2 issues of STP - Interfaces don't have to go through Listening, Learning & Forwarding states and immediately go Up when connected. There isn't the possiblily of someone screwing around with VLANs and/or other trunks on the switch and causing an STP reconvergence on the link etc.

If you must use SVI's and a trunk then make sure the bandwidth statements of the routed interfaces are correct as they will default to either 100Mbps or 1Gbps depending on which switch or router you are working on. With physical interfaces the bandwidth will be correct.

Have a read of the Layer-3 access design guide on the SRND site

http://www.cisco.com/go/srnd

HTH

Andy

Community Member

Re: Prefered method for creating routable connection between 2 s

Thanks v. much

There will be no vlans spanning between the two sites so as suggested I'll go with the routed interfaces.

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