On Thu, 2 Mar 2006, Sylvain Coutant wrote: > First, regarding Carp and STP what happens usually in a manageable L2 > switch when the same MAC is announced on two different ports ? I don't > remember that STP includes loadsharing, so isn't it possible the switch > will only choose one port to forward on ? Please excuse me if it sounds > stupid and just explain why ;-)
STP does not concern itself with MAC addresses of end-stations/ hosts / devices. It uses the MAC addresses within the networking elements that run STP to look for (and make) a loop-free network. So you problem will not be a strict STP issue. The problem you will/may encounter will differ based on the vendor of SWITCH1 and SWITCH2. Some vendors will handle it OK if the MAC is a multicast MAC, some will log a warning, some will not allow it and simple accept the first port, some will forward randomly. This is a pure vendor-implementation issue of how they forward frames and if their CAM/FDB/Forwarding Database/whatever they call it allows multiple entries and if it expires entries on ports that go down. > switches, themselves connected together through one port. That setup With all that attention to redundacy, why not make the link between SWITCH1 and SWITCH2 two links or more? > Once again, how will spanning tree handle this case with the same MAC > announced from the 4 firewalls ? My guess is packets from SRV1 will be > dispatched to FW1* because the cost will be lower. Same for SRV2/FW2*. Not an STP issue, a frame-forwarding issue on the switch. STP is not involved in end-user traffic forwarding. If you have a relationship with the vendor, ask them. Or simply try it out and report back! cheers, -- jason
