* Clifford Bailey <[EMAIL PROTECTED]> [2008-03-06 17:00]: > Hi Henning, > > Thanks for your response. Yes, your understanding of spanning tree is > the same as mine (I meant turn ON portfast at the end, not turn off > sorry!) I realize that enabling portfast is a solution, but I am still > very puzzled by why the server pauses when portfast is off as I don't > think it should make any difference. If portfast is off, the change > over shouldn't happen until the port can send and receive traffic > anyway, so that should be seemless, which it isn't.
there is your misunderstanding i think... the link goes up. carp sees that and starts sending annoucements. since stp blocks the port, they don't go anywhere. since stp blocks the port, the machine doesn't see the other machine's carp announcements either. thus, the machine becomes MASTER. so BOTH are MASTER. which doesn't matter much, since one of them is on a port that is blocked by stp. now when the port transitions to forewarding (un-blocked), both machines are still master. since they see their respective carp announcements now they'll relatively quicly elect one master and the other one goes to backup, but there is a timeframe where they are both master. one goes back to backup, one stays master. there could be an interference with the switches arp cache here as well - if the switch "learned" the mac address of the carp interface on the interface with the machine that goes to backup, it could take a moment to re-learn that address. when a carp interface becomes master, it sends out gratious arps to prevent that situation. but here both ARE master and one becomes slave, so no gratious arp. conclusion: stp and carp don't mix well :) but honestly and in any case, you should set all ports to portfast (and enable bpdu filters etc) on ALL ports that are not connected to a bridge type device (other switches, usually). -- Henning Brauer, [EMAIL PROTECTED], [EMAIL PROTECTED] BS Web Services, http://bsws.de Full-Service ISP - Secure Hosting, Mail and DNS Services Dedicated Servers, Rootservers, Application Hosting - Hamburg & Amsterdam
