[ovs-discuss] Openvswitch GRE question

Jesse Gross jesse at nicira.com
Thu Jul 21 16:35:21 UTC 2011


On Thu, Jul 21, 2011 at 11:17 AM, Roberto Sassu <roberto.sassu at polito.it> wrote:
> Hi all
>
> i'm doing some experiments with the GRE capability
> of Openvswitch.
>
> I've setup two virtual machines with IP:
>
> VM 1 (eth0): 192.168.122.119
> VM 2 (eth0): 192.168.110.142
>
> each connected to its own bridge:
>
> VM 1 -> virbr0 (192.168.122.1)
> VM 2 -> virbr1 (192.168.110.1)
>
> I've setup the host in a way that from
> one VM i can ping the other.
>
> Then i configured two bridges in the VMs with a
> GRE port and i've set their IP to:
>
> VM 1 (br0): 10.1.22.1
> VM 2 (br0): 10.1.22.2
>
> Unfortunately, i'm not able to ping the
> other VM using one of the above IP.
>
> This is the tcpdump output of VM 1 if i try to
> execute from the VM 2:
>
> ping 10.1.22.1
>
> ------
> 11:38:04.985766 IP 192.168.122.1 > 192.168.122.119: GREv0, length 46: ARP, Request who-has 10.1.22.1 tell 10.1.22.2, length 28
> 11:38:04.985826 IP 192.168.122.119 > 192.168.122.1: ICMP 192.168.122.119 protocol 47 port 25944 unreachable, length 74

GRE does a lookup on the incoming source address to identify what
tunnel the packet should be decapsulated into.  The IP that it expects
is the same as the remote_ip you configured to use to send packets.
If it doesn't find any matching tunnels then it sends an ICMP port
unreachable.

Since the sender is the address of the host and not the VM I'm
guessing that either you configured the wrong bridge or are doing some
kind of address translation.



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