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Connecting Switch to Router

Unanswered Question
Sep 20th, 2006
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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.



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glen.grant Wed, 09/20/2006 - 17:33
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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.

IM-Design Thu, 09/21/2006 - 02:31
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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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