[ovs-discuss] Setting the HW addr of bridge internal interface -- issues

[Justin Pettit]

You should be able to set it with a command similar to the following:

	ovs-vsctl set bridge br0 other-config:hwaddr=aa:bb:cc:dd:ee:ff

There are a bunch of other configuration parameters you may want to look at here:

	http://openvswitch.org/ovs-vswitchd.conf.db.5.pdf

Hope that helps.

--Justin


On Dec 25, 2012, at 11:43 PM, Florian Daniel Otel <florian.otel at gmail.com> wrote:

> Hello all, 
> 
> First, a disclaimer: As I'm relatively new to OVS (and to this list) pls point me to the correct resource(s) if this is a known issue / solution.  TIA. 
> 
> Setup: 
> 
> I am trying to do some testing with OVS inside a VM.  The challenge is that in the environment I'm working the Host does a static mapping btw. the MAC address of  VM's primary interface ("eth0" henceforth) and the  ip address it assigns to that VM. Since my tests involve putting that primary interface ("eth0")  in an OVS bridge as per the OVS standard FAQ I need to first zero out the ip address of the said interface, add  "eth0" to my bridge and then assign "eth0" ip address  to "br0" -- i.e. to the bridge internal interface (then reset the default gateway etc. etc accordingly...)
> 
> Now, given the peculiarities of my setup that swap doesn't work straight away since the MAC addrs of "eth0" and "br0" are different, so the connectivity to the outside world is cut off by the host (it still responds to e.g. ARP traffic by sending the responses to "eth0" MAC address). 
> 
> The way I solve this is not only to assign to "br0" the  IP addr of  "eth0"  but swap MAC addresses as well btw the two interfaces, using smth like this: 
> 
>         OLDHWADDR=`cat /sys/class/net/eth0/address`
>         NEWHWADDR=`cat /sys/class/net/br0/address`
>     
>         ifconfig eth0 down
>         ifconfig eth0 hw ether $NEWHWADDR
>         ifconfig eth0 up 
> 
>         ifconfig br0 hw ether $OLDHWADDR
> 
> As a result "br0" has "eth0" IP _and_ MAC addrs, and all works well. 
> 
> Problem: 
> 
> As soon as I do _any_  subsequent operations in OVS -- e.g. add another (unrelated)  bridge "br1" , add a port to "br1" etc. etc -- the MAC address of "br0" is  reset to its initial value. Which, given my setup, cuts off the VM from the outside world again. 
> 
> Questions:
> 
> 1) Is this intended behavior ? If yes, any logic behind it and can that be altered ? 
> 
> 2) How can I make the MAC address assignment to a bridge internal interface "stick" i.e. make it a one time only operation  ? 
>    Goes w/o saying that, while I can script any subsequent  OVS operations by appending them with a command that re-sets the "br0" MAC addr to the one I need to, that's nothing short of a horrible workaround..
> 
> I've confirmed this behavior on Ubuntu 12.04 x64 with both vannilla packages (1.4.0.1-1ubuntu1.3) and the code currently in the official GitHub repo.  LMK if there is any more info needed. 
> 
> TIA for all the help / advice / pointers,
> 
> Florian _______________________________________________
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