[Bridge] Cannot ping to the board when changing loop configuration

Patrick Bogen pdbogen at tamu.edu
Tue Jan 11 08:37:05 PST 2005

Hash: SHA1

Prashant Agrawal wrote:
| Hi all,
| I am running a bridge with STP 'on' on an arm-linux
| board. I have two ethernet ports on the bridge both
| connected to a single switch thus creating a loop.
| Using brctl on the board, I can see one of the port
| being blocked and the other forwarding. I can ping the
| board from a remote PC connected to the same switch.
|     _______ 1       _______       ____
|    |       |-------|       |_____|    |
|    | Board |xxx----|Switch |     | PC |
|    |_______|2      |_______|     |____|
| When I disconnect the cable from the forwarding port
| (port 1), I can see both the ports going into the
| forwarding state. However, when I try to ping the
| board again from the remote PC, I am not able to reach
| the board anymore. Sniffing the packets show that the
| board can receive arp requests on the port 2 but the
| arp response is not generated. Sniffing packets on the
| bridge interface show arp queries being sent to PC
| instead.
| Please help.
| --Prashant
It's possible I'm making this up, but could it perhaps be that the STP code is
detecting the loop and changing things to "fix" it? Does it work with STP turned

- - Patrick Bogen
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