Alex Bligh alex at
Mon Oct 6 07:39:03 UTC 2014

On 6 Oct 2014, at 07:54, Ellad G. Yatsko <eyatsko at> wrote:

> Maybe this question have already "set your teeth on edge". :-) But...
> I wonder how to set up ISC DHCPD to be Cisco VRF aware when
> IP Pools are overlapped.
> For example:
> VRF_A has    and
> VRF_B has
> I know all about option 82, but I can't use it because ISC DCHP doesn't
> allow to introduce in its configuration neither overlapped subnets nor
> overlapped pools.
> What to do?

Not recommended unless you really know what you are doing, but you
can get around /some/ of the issue here simply by giving your
server a subnet of 0/0 - overlapped subnet issue solved. You
can then select fixed addresses based on option 82 I guess.
I suspect you need the same approach with the pool (i.e.
one pool).

Your problem is that the VRF is really running 2 IP networks
(rather than one), but dhcp doesn't similarly virtualise.
You thus really need 2 dhcp instances. An easy-ish way to
do this would be to use docker or lxc to put them in
different containers, listening on their own veth
interface bridged your ethernet VLAN.

Alex Bligh

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