Hi.
Version info first: This is from the 2.6.10 kernel, but I have not
found any relevant changes in later kernels. On the other hand, the
network subsystem has always caused me headaches whenever I try to
follow what happens. :)
I've run into what probably is a policy decision, but I cannot quite get
the reason: When sending TCP traffic to a machine, the first packet
will cause an arp request to be made. Later on, this arp entry gets its
lifetime extended by the TCP packets, so that it does not have to arp
again until the network becomes quiet.
But if i ping the machine, thus sending only ICMP and no TCP traffic,
the arp entry will time out every 30-45 seconds, and it has to re-arp
for the next packet. As far as I can tell, the ICMP handlers does not
update the arp entry, and I really cannot understand why (not).
Usually this is not a big problem, it just causes some extra arp
traffic. In my case though, we have an application monitoring the arp
events trying to do some "smart" stuff wrt. routing etc. And it would
be easier if we could assume that an arp entry that disappears does that
because there is no traffic using it. :)
I hope this made sense...
-Harald
--
Harald Nordgård-Hansen, AXXESSIT ASA
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