[CentOS] CentOS-6.7, kvm bridges, virtual interfaces, and routes

Fri Jan 8 17:49:59 UTC 2016
Tony Mountifield <tony at softins.co.uk>

In article <55ae6ce7fe2cbdba1514f1072281c006.squirrel at webmail.harte-lyne.ca>,
James B. Byrne <byrnejb at harte-lyne.ca> wrote:
> I have been looking at this problem on and off for a considerable
> period.  Given my lack of knowledge I have been unable to resolve this
> quickly and in consequence it has been constantly shoved to the
> background as other issues arise.
> Here is the situation:
> An ASCII art diagram might help, or might not.
> <pre>
> kvmh1g1           eth0/
>                   eth1/aaa.bbb.ccc.151 <-------------> |
>                                                        |
> kvmh1             br1/aaa.bbb.ccc.51                   |
>             |---> br0/                     |
>             X                                          |
> kvmh2       |---> br0/                     |
>                   br1/aaa.bbb.ccc.52                   |
>                                                        |
> kvmh2g1           eth0/                    |
>                   eth1/aaa.bbb.ccc.251 <-------------> |
>                                                        |
> gateway           eth1/aaa.bbb.ccc.1 <---------------> |
> </pre>

Why are you using two separate subnets, and
That is the core of your problem. You can't use a crossover cable between
different subnets; you would need a router. There may be an esoteric way,
but it's not a normal configuration.

But they don't need to be different subnets at all. Logically speaking, they
are the same subnet.

So give kvmh1:br0 and kvmh2:br0 Then they can
talk to each other easily, without doing anything special.

On the guests, give them and 192.168.12 (for example).
I don't think they should use the same IP addresses as their hosts.

Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org