Date: Sat, 22 Oct 2011 00:10:05 +0000 From: "Li, Qing" <qing.li@bluecoat.com> To: Steven Hartland <killing@multiplay.co.uk>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: RE: very strange arp problem after ip move - icmp works udp doesn't Message-ID: <B143A8975061C446AD5E29742C53172315C5C1@PWSVL-EXCMBX-01.internal.cacheflow.com> In-Reply-To: <02FFC9CF360C4E2F81B00B653DE1584E@multiplay.co.uk> References: <02FFC9CF360C4E2F81B00B653DE1584E@multiplay.co.uk>
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You don't have the flowtable component enabled, do you ?=0A=
=0A=
--Qing=0A=
=0A=
________________________________________=0A=
From: owner-freebsd-net@freebsd.org [owner-freebsd-net@freebsd.org] on beha=
lf of Steven Hartland [killing@multiplay.co.uk]=0A=
Sent: Friday, October 21, 2011 4:44 PM=0A=
To: freebsd-net@freebsd.org=0A=
Subject: very strange arp problem after ip move - icmp works udp doesn't=0A=
=0A=
After a HD failure we moved an IP of one of our DNS=0A=
servers to some new hardware.=0A=
=0A=
Now we are seeing some very strange behaviour on a number=0A=
of machines when talking to the ip which was moved.=0A=
=0A=
Specifically it seems both icmp and tcp work just fine=0A=
but udp doesn't.=0A=
=0A=
I've just done a trace from one such box and to my horror=0A=
the tcpdump shows icmp and udp traffic for the same=0A=
IP going to different mac's.=0A=
=0A=
icmp is going to the right mac and is working fine=0A=
but udp is going to the wrong mac and isn't (as you=0A=
would expect)=0A=
=0A=
In /var/log/messages there are arp messages=0A=
which show the ip moving from -> to the correct macs=0A=
but it seems like something somewhere is caching=0A=
the resolution.=0A=
=0A=
arp -a also show's the correct result and arp -d -a doesn't=0A=
help.=0A=
=0A=
So the question how on earth is udp resolving the mac=0A=
to something different than icmp and tcp?=0A=
=0A=
To complicate matters even further some machines are=0A=
working intermittently and the traces show the udp=0A=
some times going to the right place and some times=0A=
not.=0A=
=0A=
In all tests we're using just a dig with a specified=0A=
server.=0A=
=0A=
The machines involved are all running 8.2-RELEASE on=0A=
amd64=0A=
=0A=
Any help would be most appreciated as its causing chaos=0A=
due to the IP that moved being our DNS servers and hence=0A=
things are randomly stalling left right and center :(=0A=
=0A=
Regards=0A=
Steve=0A=
=0A=
=0A=
=0A=
=0A=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=0A=
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