multipath routing and destination selection

From: Aleksandar Ivanisevic
Date: Wed Feb 10 2010 - 11:15:09 EST



Hi,

please redirect me to the proper place if this is not the right group
for this kind of question.

my kernel is 2.6.18-164.11.1.el5, so latest centos 5.4. I have a
multipath route defined as:

$ sudo /sbin/ip route show table 199
default mtu 1496
nexthop dev ppp3 weight 1
nexthop dev ppp4 weight 1
nexthop dev ppp5 weight 1

According to the docs next hops should be assigned per-flow, which
means each source/destination pair, right?

My problem is that every 60 seconds or so the route cache gets
discarded, no matter if there is an existing connection or not. Most
of the time new interface gets assigned to the flow causing all
connections longer than 60 seconds to break at that point.

Is this how it is supposed to work? Tried playing with sysctl entries
under net.ipv4.route.gc_* but failed. No matter what I do, routing
cache gets thrashed every 60 seconds.

Is there a way to say: I want every source/destination pair to
initially get a random nexthop but then stick to it unless it doesn't
exist any more or the cache is manually flushed.

Thanks.

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