On Thu, May 8, 2008 at 8:01 AM, Joakim Tjernlund <joakim.tjernlund@xxxxxxxxxxxx> wrote: > > On Thu, 2008-05-08 at 02:16 +0000, richardvoigt@xxxxxxxxx wrote: > > On Wed, May 7, 2008 at 9:22 AM, Joakim Tjernlund > > <joakim.tjernlund@xxxxxxxxxxxx> 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. > > I see, would it hurt something else if STP did turn off it interface in > this case? Optical i/f's is getting more common so these types of loops > will increase so I think this needs to be addressed. Yes, it would hurt. For example, this topology: br0 - br1 - br2 - br3 - br1 There is a loop in br1-br2-br3-br1, so br0 sees its packet come back on the same interface. If br0 shuts down the interface, it breaks connectivity. The br0-br1 link is part of a minimal spanning tree so STP cannot shut it down. There is no way for STP to distinguish your case, which is misconfigured, from this example, which is a valid use of redundant links. _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
