2013/12/5 Antonis Manousis <[email protected]> > Hey everybody, > After reading the man page of carp (4) and since I am currently working > with this protocol I have a question concerning the first bug mentioned > in the bug section and a more general one. I quote from the man page.. > > If load balancing is used in setups where the carpdev does not share an > IP in the same subnet as carp, it is not possible to use the IP of the > carp interface for self originated traffic. > If I understand this sentence well, it is not possible to use load > balancing in > cases where the carpdev does not have a static IP since by design both the > CARP interface as well as the physical interface have to be in the same > subnet. > Is that true? >
You probably want that anyhow, in any case where other shared resources (smtp, syslog, ntp) are to be reached over a interface where carp lives, so you might aswell get used to the idea of having "real" ips on the physical interfaces on which carp then has a third shared ip that moves with the MASTER role. > My second question is more about the way carp advertisments are exchanged > between hosts. All the traffic that has to do with carp's control messages > passes > through the physical interfaces carp interfaces are bound to. What is the > rationale > behind this decision? > If you have BoxA <--shared-medium--> BoxB and the shared medium breaks, you would not notice that unless you send a heartbeat over that same shared medium, which is exactly what carp does. If you carp on several different shared media, then you send announcements over each one of them. > Would it be possible to redirect this traffic over a dedicated network from > another interface of the machine that uses carp? > Perhaps. But it would completely destroy any use of the shared carp ip as a way to handle network failovers, would it not? As long as the dedicated network is functioning, the carp would never transition from BoxA to BoxB since the slave would always consider the master to be reachable and working. -- May the most significant bit of your life be positive.
