carp on multiple interfaces

[Gergely CZUCZY]

Hello

This question just popped out of my head today when playing
around with linux's LVS and keepalived.

On a dual-carp scenario on two gateways when both the internal and
the external IFs are carp(4)'d in a master-slave way and a link
disconnects only on one side, would this trigger a carp failover
of the other interface also?

Like in the local side 10.0.0.{1,2} are the IF IPs and .3 is the
carp IP, whereas the 1.2.3.{1,2,3} IPs are respectively the public
IF and carp IPs. If the link on the IF of 1.2.3.1 goes DOWN, then
the 1.2.3.3 should be failed over to the .2(slave) box, right?
Now, on the local side still the .1(master) box has the carp'd IP
because everything works fine in the LAN carp setup.
This would turn out to be a tricky situation, because the local clients
would get network-unreachable because the default local gateway had lost
its outgoing connection, and the incoming connections would also time out
because the clients would send the SYN+ACK replies over the master box,
whereas that had lost its outgoing connection.

Am i right that the FreeBSD carp(4) implementation has this issue?
I don't have the opportunity to try this at the moment, but I'm interested
in the way it would behave in a scenario like this. Had anyone met this
already? Are there any workarounds/solutions for this?

Thanks in advance

Sincerely,

Gergely Czuczy
mailto: gergely.czuczy at harmless.hu

-- 
Weenies test. Geniuses solve problems that arise.
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