Same MAC address on two VLANs & subnets

[Gerald Vogt]

On Fri, Feb 24, 2012 at 3:38 PM, John Wobus <jw354 at cornell.edu> wrote:
> On Feb 16, 2012, at 11:58 AM, Gerald Vogt wrote:
> I'm actually writing to mention that there exists network
> equipment that does not handle the same mac address on
> two VLANs, and depending upon what you've checked out
> in that regard, its conceivable that that is causing
> problems.  I also wouldn't trust a DHCP client until I'd
> sniffed it.

The network handles the same MAC address on multiple VLANs properly.
All DHCP messages are sent to the correct VLANs and are received on
the correct VLAN on the server side.

It's definitively the server: the very moment it receives a
DHCPDISCOVER on the other VLAN/subnet it releases the lease in the
other subnet. I can see it in the dhcpd.leases file: it first writes
an "binding state released" entry for the already active lease
10.10.10.5, immediately followed by the new active lease for the
second subnet 10.20.20.8. The client definitively does not release the
10.10.10.5 address not does the server receives any other messages but
the DHCPDISCOVER and DHCPREQUEST for the second address on the second
VLAN.

I can only find that it's the server which releases the first lease
because the client uses the same client identifier to obtain the lease
on the second subnet. I am puzzled if others are able to discover two
leases in two subnets using the same client identifier. I can't see
that at least for 4.2.3-P2.

Thx, Gerald