[ovs-discuss] Issues with ARP across hosts connected with GRE tunnel

Shridhar Sahukar shridhar.sahukar at cyaninc.com
Mon Jul 14 23:22:25 UTC 2014


Hi,

On my setup, I have 2 hosts connected with a GRE tunnel with following
configuration:

Host 1:

#ovs-vsctl add-br br0
#ifconfig br0 1.1.1.1
#ovs-vsctl add-port br0 gre0 -- set interface gre0 type=gre
options:remote_ip=<eth0 ip of host2>

Host 2:
#ovs-vsctl add-br br1
#ifconfig br1 1.1.2.1
#ovs-vsctl add-port br1 gre0 -- set interface gre0 type=gre
options:remote_ip=<eth0 ip of host1>

As you can see, bridge 0 on host-1 and bridge 1 on host-2 are in different
subnet and I am trying to connect them with a GRE tunnel.

This setup works as expected for all other purposes, except that during the
initial setup the ARP communication does not happen as expected.

Most of the times, when we ping bridge0 IP from host2 or bridge1 IP from
host1, the ping does not work. tcpdump on the eth0 interface shows incoming
ARP requests, but I dont see any ARP responses going back. At this point,
if I initiate a reverse ping then everything starts working.

It seems that the ARP requests are not getting forwarded to the bridge from
the GRE interface. Do I need to add any special flow?

Any help is much appreciated.

Thanks,
Shridhar
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