DHCP server with multiple VLANs

[Ecagle]

I am using all ProCurve switches and I have a network with two VLANs (1 and 30).  Routing is being performed by my gateway router.  DHCP is being provided from a Windows Server with a DHCP scope for each VLAN.  The core switch has the router plugged into port 1 and tagged for both VLAN 1 and 30.  The other ports on the switch are untagged for VLAN 1 and tagged for VLAN 30.  If I plug the server into any port configured this way, it only gives out a VLAN 1 address and not a VLAN 30 address.  However, I discovered that if I plug the server in to an secondary switch that is configured with all ports as untagged for VLAN 1 and do not create any additional VLANs that everything works as expected.

My question is how to configure a port on the primary switch so that I do not need the secondary switch to make the DHCP work correctly.

Thanks for any input with this...

P.S. This thread has been moved from Switches, Hubs, Modems (Legacy ITRC forum) to ProCurve / ProVision-Based. - Hp Forum moderator

[Vince-Whirlwind]

Servers tend to have NICs that are 802.1q capable, so even though you might only have a VLAN1 IP address configured on it, if there is a tagged VLAN on its switchport, the server will also receive all traffic from VLAN30, although lacking an IP address in VLAN30, it will reply on VLAN1.

In the case of DHCP, the server will see a DHCP request twice: first, directly off VLAN30, then secondly via the IP helper address configured on the VLAN30 interface on the router.

The solution to this is to ensure the Server is not patched to a switchport that has any tagged VLANs assigned to it.