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New Member

Multinet or new VLAN

Company wants to move all DHCP for computers and voice to a new Windows DHCP server from Linux. Right now the DHCP pool at headquarters is - and there are servers on that same subnet. They want to use as a new pool and ditch - leaving that for only servers. Below is the switch and router info.

Company has and on VLAN 100 which is their access vlan at their headquarters


 Access VLAN 100
 Voice VLAN 10

 VLAN 10
  ip address
  ip helper-address

 VLAN 100
  ip address secondary
  ip address

 We are moving from a Linux DHCP that has two addresses:

NOTE: I do not know why it has 2 addresses. All IP helpers at the remote locations point to


 Interface Gigabit0/0.100
  IP Address
  IP Address 192.168.8./1 (secondary)


Would I just add another address to VLAN 100 ( and another address to the 0/0.100 interface ( to the router then an IP helper on VLAN 100 on the core switch to point to (new DHCP server)? I'd also modify the VLAN 10 IP Helper to point to

Or, would it be better to create another VLAN and modify all the switchports "access" VLAN's via the appropriate Macro/individual switchport? I suppose I'd also have to add all the routing as well as a new sub interface on the router like 0/0.80 and add the new VLAN to all the trunks if this were done as well.

Thanks in advance.

New Member

Change the IP of VLAN 100 and

Change the IP of VLAN 100 and the corresponding g/w address on the router, that way you don't need to move ports.

Create another VLAN for the servers, you will need to create a sub interface for the same on the router.

Correct, you need to specify the address of the DHCP server via 'IP Helper', as by this plan, the DHCP server will be in the server VLAN.

Remember to add your new g/w address to your DHCP configuration.

You don't need to change any routing!

The interface that connects to the router needs to remain as a trunk.

You would only need to add the new VLAN to the trunk, if you have only allowed certain VLAN's, by default all are allowed.


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