[Ilugc] Weird network problem
- From: girish1729@xxxxxxxxx (Girish Venkatachalam)
- Date: Mon Jul 31 13:45:03 2006
--- Joe Steeve <joe_steeve@xxxxxxx> wrote:
Girish Venkatachalam wrote:
ARP cache might be getting corrupted.
Execute this on ur mailserver as root.
# arp -d 203.129.194.201
might do the same thing as ifdown , ifup on the
mailserver. If this
solves the problem then at least you know what the
problem is.
But., there is no way the mailserver would know the
MAC address of
203.129.194.201. There is another router in the
middle (the cisco
router) which routes traffic other than the subnet
203.129.194.16/28 to
the ISP router. And when the issue occurs on the
mailserver., all other
machines (except the mailserver) work fine. So that
means the ARP of the
cisco router is fine.
Try clearing the ARP caches completely once in a
while. You can try clearing the Cisco router ARP entry
then.
Other than that what does ifdown/ifup do? It might do
much more but this seems to be a good reason to me.
One good thing to do would be to figure out how often
ur mail server talks out on the network. Dumping
tcpdump to a file and analyzing what goes wrong when
would help.
Networking problems can get really hairy. I suggest
you analyze your problem using as many tools as
possible.
First analyze all packet data using a good sniffer
like tcpdump. Figure out a patten between when this
problem comes and the packet sequence just before
that.
Once we have data and zero in on the problem then the
workaround/ solution can always be worked out.
HTH,
Girish
--
.o. A proud GNU user
..o
ooo [W] http://www.joesteeve.org/
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