Well first, you can have separate DHCP servers as long as they are on:
a) Separate subnets
b) serving different scopes
That in mind, if you have a dhcp scope on your 3750, you would need a vlan interface that is addressed in that same scope:
int vlan 50
ip address 192.168.50.1 255.255.255.0
ip dhcp pool VLAN50
network 192.168.50.0 255.255.255.0
default-router 192.168.50.1
dns-server 4.2.2.1
On the OTHER DHCP server that you want to get your addresses from, you would need a separate VLAN interface configured with an IP address like:
int VLAN 100
ip address 192.168.100.1 255.255.255.0
ip helper-address 192.168.100.50
Anything coming in on VLAN 100 will go to the 192.168.100.50 to get an address. You would need a pool for 192.168.100.0 on the DHCP server for that.
I wouldn't recommend using separate DHCP servers though because you can use just the one DHCP server (Linux/Windows) to serve multiple scopes. All VLANs in your switch would have the helper-address assigned as your one DHCP server.
int vlan 50
ip address 10.50.1.1 255.255.255.0
ip helper-address 192.168.100.50
int vlan 225
ip address 172.22.225.1 255.255.255.0
ip helper-address 192.168.100.50
int vlan 322
ip address 192.168.32.1 255.255.255.0
ip helper-address 192.168.100.50
On the DHCP server, you would have:
Scope
10.50.1.0
172.22.225.0
192.168.32.0
You would set all of your options that you need to assign under those scopes.
HTH,
John
HTH,
John
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