On Tue, 2008-05-13 at 03:10 +0000, richardvoigt@xxxxxxxxx wrote: > 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. Once STP has dealt with the loop in br1-br2-br3-br1 and disabled one of the br1 interfaces, br0 won't see its own pkgs and start forwarding again, right? My use case is a common one in optical transmisson equipment. This is what you do to test connectivity, troubleshoot etc. and it would be nice if STP could deal with it. Jocke _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
