vlans and dhcp superscopes

Danny Mainprize · ‎04-10-2017

Is there a way to allow 1 vlan to get addresses from a superscope with multiple scopes in it?

Vlan 101 - default gateway is 10.0.101.1

I want to have a DHCP superscope with 10.0.101.2-250 and 10.0.105.2 - 250. I can create the superscope no problem, I am just not sure what to point my ip dhcp relay command at on the switch. The switch is a 3650X and the dhcp server is a MS Server 2012R2.

Basically I need to combine two discontinuous dhcp pools with a single gateway address. Normally I would just kill all the old DHCP scopes and build it right, but my problem does not allow me that luxury.

lpassmore · ‎04-10-2017

Hi Danny

You haven't really said what the IP address associated with VLAN 101 is, but to do what you want you will need to configure it something like this:

int vlan101
  ip address 10.0.101.1 255.255.255.0
  ip address 10.0.105.1 255.255.255.0 secondary
  ip helper (your DHCP server address)

ip dhcp smart-relay

This will try first to send the request to the server using the main IP address and then if it doesn't see a DHCP offer come back it will try again using the secondary address