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

Gurucharan Shetty shettyg at nicira.com
Mon Jul 14 23:54:02 UTC 2014


On Mon, Jul 14, 2014 at 4:22 PM, Shridhar Sahukar
<shridhar.sahukar at cyaninc.com> wrote:
> 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.
I suppose you have set the netmask properly. Otherwise they are in the
same subnet.
Assuming they are in different subnet, you will probably need routing
table entries.


>
> 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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