Open Stack

Hi

I have an interesting use case for quantum networking

This is the example :

Server A eth0 10.1.1.1 (http proxy)
Server B eth0 10.1.1.2 (runs LXC VM's)
Server B lxc-br 10.1.2.0/24 (the LXC's get addresses here)

Server A and B run OSPF so server A knows 10.1.2.0/24 is behind 10.1.1.2.
(We have more than just A and B hence the useage of OSPF)

If I ping 10.1.2.1 from Server A it fails.
If I ping Server A from a VM with IP 10.1.2.1 then it works, however looking
at the tcpdump the source of the VM's ICMP is rewritten to Server B's eth0
address.

Digging a bit deeper I see this on Server B when pinging from Server A to an
LXC

tcpdump -i eth0 host 10.1.2.1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
13:49:52.850764 IP 10.1.1.1 > 10.1.2.1: ICMP echo request, id 25672, seq
387, length 64
13:49:52.850878 IP 10.1.2.1 > 10.1.1.1: ICMP echo reply, id 25672, seq 387,
length 64
13:49:53.850600 IP 10.1.1.1 > 10.1.2.1: ICMP echo request, id 25672, seq
388, length 64
13:49:53.850710 IP 10.1.2.1 > 10.1.1.1: ICMP echo reply, id 25672, seq 388,
length 64

And this is what I see on Server A

tcpdump -i eth0 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
13:53:41.852613 IP 10.1.1.1 > 10.1.2.1: ICMP echo request, id 25672, seq
616, length 64
13:53:42.852603 IP 10.1.1.1 > 10.1.2.1: ICMP echo request, id 25672, seq
617, length 64

So the ICMP is getting to the VM without being rewritten, and the reply is
being sent to Server A but something is dropping it in transit - I suspect
its Open vSwitch GRE...

If anyone can shed any light on this and if there is something I can do to
stop this that would be awesome, We have been doing the on AWS however we
have had to create GRE tunnels there inside the instances to make it work,
We would love it if we didnt have to do that :)


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