[ovs-discuss] VLAN unable to ping

Ben Pfaff blp at nicira.com
Sun Dec 8 15:29:30 UTC 2013


On Sun, Dec 08, 2013 at 02:45:46PM +0000, Phil Daws wrote:
> have set up OVS on a test system, with KVM, and created a couple of
> VLAN's. From what OVS is showing me:
> 
> uxbod-office qemu # ovs-vsctl show 
> 76d53621-7bf2-4af2-b24c-181a016317d7 
> Bridge "ovsbr0" 
> Port "vnet1" 
> trunks: [2] 
> Interface "vnet1" 
> Port "ovsbr0" 
> Interface "ovsbr0" 
> type: internal 
> Port "vnet3" 
> trunks: [2] 
> Interface "vnet3" 
> Port "eth0" 
> Interface "eth0" 
> Port "vnet0" 
> trunks: [0, 1] 
> Interface "vnet0" 
> Port "vnet2" 
> trunks: [0, 1] 
> Interface "vnet2" 
> ovs_version: "1.10.2" 

This would be much easier to read if you had preserved the indentation.

> interfaces vnet1 and vlan2 should be able to ping each other, yet they
> cannot. They appear to be configured okay:

I guess you mean vnet2, since you have no vlan2.

> Am I missing something blatantly obvious please ? 

You configured vnet1 to trunk VLAN 2.
You configured vnet2 to trunk VLAN 0 and 1.
Therefore, it should be blatantly obvious that vnet1 and vnet2 cannot
talk to each other.

Q: I added a pair of VMs on different VLANs, like this:

       ovs-vsctl add-br br0
       ovs-vsctl add-port br0 eth0
       ovs-vsctl add-port br0 tap0 tag=9
       ovs-vsctl add-port br0 tap1 tag=10

    but the VMs can't access each other, the external network, or the
    Internet.

A: It is to be expected that the VMs can't access each other.  VLANs
   are a means to partition a network.  When you configured tap0 and
   tap1 as access ports for different VLANs, you indicated that they
   should be isolated from each other.

   As for the external network and the Internet, it seems likely that
   the machines you are trying to access are not on VLAN 9 (or 10) and
   that the Internet is not available on VLAN 9 (or 10).



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