[ovs-discuss] How to make Open vSwitch a router

Justin Pettit jpettit at nicira.com
Wed Nov 10 07:06:36 UTC 2010


On Nov 9, 2010, at 9:06 PM, Derek Cormier wrote:

> Thanks for your reply Jesse, my comments are inline.
> 
> On 11/10/2010 01:31 PM, Jesse Gross wrote:
>> On Tue, Nov 9, 2010 at 7:52 PM, Derek Cormier
>> <derek.cormier at lab.ntt.co.jp>  wrote:
>>   
>>> *My apologies, the formatting of my diagram got messed up after I sent it. I
>>> think it still gets the point across thought, vm1 and vm2 are connected to
>>> br0 and vm3 is connected to br1.
>>> 
>>> @Martin: I see. Do you know if anyone has tried this before?
>>>     
>> I doubt it.  For one thing, OpenFlow 1.0 doesn't provide the ability
>> to modify the TTL, so it's not actually possible to create a standards
>> compliant router, short of sending all packets to the controller.
> 
> Couldn't you modify the contents of the packet with NOX?

That's what he meant by sending all packets to the controller.

>>> Something I'm a bit confused about: When you plug an Ethernet cable into a
>>> router, the router's NIC has an IP address. In the case of Open vSwitch,
>>> does that interface correspond to the IP address of the bridge?
>>>     
>> Open vSwitch is modeling a switch and switches don't have IP addresses
>> on their ports.  The IP address of the bridge is essentially a switch
>> port that is directly attached to the host OS.  
> 
> Could you please give an example of when you would need to assign an IP address to a bridge?


If all the ports on your systems are attached to a bridge, then there would be no way to connect to the box if you don't assign an address to the bridge, since the ports can't have IP addresses.

--Justin






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