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Community Member

Connecting Switch to Router


I have a 3750 switch that has several VLANs defined on it. I also have an 1841 router that has the same VLANs defined (they are numbered the same).

At the moment they are connected and I am able to browse from a host connected to the default VLAN. I would like to connect the switch to the router and test the VLAN functionality.

Where do I start? On the switch or on the router

When I tried to complete the LAN wizard on the router and assign the default VLAN to the routers Fa0/0/0 port, it caused the switch Gi port to err-disable due to bpduguard.



Community Member

Re: Connecting Switch to Router

Found this link, but Im not sure it applies to my situation ass the hardware combination is different.

Can anyone confirm that the methods mentioned herein would work for my hardware:

Switch: 3750G 12.2(25)SEB4

Router: 1841 29.4(9) T1



Re: Connecting Switch to Router

Sounds like your router may have like a 4 port switch card built in , if you have bpdu guard on your 3750 then it will shutdown the port because the router swithcard will send bpdu's down the link . You may have to shut bpdu guard off on that connecting link. if you are trying to trunk off a 4 port hwic switchcard then that setup is a little different and more involved than using subinterfaces on a regular router interface.

Community Member

Re: Connecting Switch to Router

Yes I am connecting the switch and the router via Gi1/0/1 on the switch and Fa0/0/0 on the router. The Fa0/0/0 is one of 4 ports on the router switchcard HWIC.

Is there a configuration document for this type of setup?

Also, the switch did shut down the port with a reason of BDPU... so it seems likely that the switch shut down the port because the router was sending bpdu's. What is the risk in shutting down bpduguard? Do I need to shut it down on the router switchcard as well as on the switch?

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