[Bridge] STP bug, loop not detetcted

richardvoigt at gmail.com
2008-05-08T02:16:18Z

On Wed, May 7, 2008 at 9:22 AM, Joakim Tjernlund
<joakim.tjernlund at transmode.se> wrote:
> Got a bridge with 4 optical VLAN interfaces, eth1.1, eth1.2, eth1.3 and
>  eth1.4, attached and the builtin STP enabled. eth1 is connected to
>  a "switch" with 4 real interfaces, each real interface maps to
one of
>  the above mentioned VLANs.
>
>  If I loop two or more interfaces by connecting each interface's output
>  to its own input, I get a loop that STP doesn't detect.
>  Looping by connecting an output from one interface to another interface
>  input works fine.
>
>  Bug or limitation in STP? If limitation, would RSTP help here?

Limitation in STP.

If a bridge receives one of its own STP packets on the same interface
from which it was sent, that indicates a loop elsewhere in the network
that disabling an interface locally will not fix, therefore STP takes
no action.

>
>  Kernel 2.6.25
>
>   Jocke
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