Subinterfaces on Router

Unanswered Question
Feb 29th, 2008

I created 3 subinterfaces on a 3800 router for VLANs on different switches but the subintefaces protocl shows "down" {see attached for output}. Can someone tell me what I missing?

Thanks in advance,


I have this problem too.
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Jon Marshall Fri, 02/29/2008 - 08:50


What is the gigabit interface connected into at the other end. It should be a switch and the port on the switch needs to be configured as an 802.1q trunk.


Edison Ortiz Fri, 02/29/2008 - 08:52

The physical interface is down, verify cabling.

What device is this physical interface attached to?

Can you post the configuration for the physical interface on this router and the device it's attached to?



skhirbash Fri, 02/29/2008 - 09:25

The router's phyiscal interface is connected to a trunk port on a 3560 switch. The port has been verified to be configured properly. Attched is the output of the port status on that switch.

Jon Marshall Fri, 02/29/2008 - 09:53

Okay, can you

1) check speed/duplex settings on both the 3800 and the 3560 switch

2) Try a different cable.

3) Post full interface configuration from router


skhirbash Fri, 02/29/2008 - 10:10

I replaced the path cord and everything worked fine. I should have checked the patch cord first but I didn't since the same patch cord and setting was working fine with a different switch.

Thanks so much for your efforts.



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