On Thu, Oct 1, 2009 at 2:02 PM, Timo Schoeler <timo.schoeler at riscworks.net>wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Hi list, > > I have a weird (?) problem here on a setup running CentOS 5.3 x86_64 > (and OpenVZ, and some home-brew L2TP daemons, RIPd, BGPd, etc). > > There's a (VE in OpenVZ speak) virtual machine that has two ethernet > interfaces, seen as eth0 and eth1, respectively. Those live in VLANs, > but it's not important here. > > The thing is that on eth1 the default route lives, while on eth0 all > traffic comes in. > > So, sending a ping to the IP address of eth0 tcpdump shows that the echo > request (type 8) packet arrives on the machine. However, the machine > does _not_ send an echo reply (type 0) back to the machine that pings > eth0, maybe because it would have to emerge from eth1. > > One exception (an obvious one) is that IPs on the /29 where eth0 lives > on _can_ ping eth0 and receive an answer -- this is because the packets > don't have to take 'the default route', which lives on the other > interface, eth1. > > This seems to me like decent behaviour. > > However, I really need eth0 to be able to be pinged from the outside > world, it's totally okay for me that eth1 would 'answer' and send the > echo replies instead of eth0. > > Is there anything I can tweak (via sysctl or whatever)? > You need a way to tell that packets originating from eth0 destined outside should be routed to eth0. This thread should help: http://lists.centos.org/pipermail/centos/2009-January/070828.html Giovanni P. Tirloni tirloni at gmail.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos/attachments/20091001/35021e4c/attachment-0004.html>