Question : Cisco - IP helper for a specific vlan

I have a Cisco 6509 running 12.1 IOS - its the core switch on the network.

It has multiple ultiple Gigabit Ethernet ports on it, each of which is connectect to 3550 switches located on each floor of our building.

Each of the gigabit eithernet ports has two VLANs configured on it - hence the port is in trunk mode.

Imaging that on the 3350 I want to have two vlans (Vlan 1 using 192.168.50.x with a gateway of 192.168.50.1 assigned to the Gb port on the 6509 and Vlan 2 using 192.168.5.x with a gateway of 192.168.60.1) on the Gb port of the 6509.  Each port on the 3550 is in both vlan 1 and 2 - vlan 1 is untagged, while vlan 2 has tagged devices (ip phones)

I have configured an IP helper so that when a user boots up on the 3550 and they are in vlan 1, they hit the helper and their dhcp request is answered by a DHCP scope which has the gateway address 192.168.50.1

What I need to know is how to I configure the 6509 so that when it receices a dhcp request  from a device that is tegged to vlan 2 that dhcp request is answered by the relevant scope on the dhcp server.  

I guess my question is based on my assumption that the dhcp server works out which scope should answer a request by loohing at the gateway from which the request has been received.

Any suggestions or pointers would be great.

Answer : Cisco - IP helper for a specific vlan

Please look at the VOICE VLAN configuration options for the switchport.  It looks to me like you use a typical VLAN assignment for data and then a Voice VLAN assignment for the phone.  The switch trunks these tagged packets back to the 6509, which handles them accordingly.