I made a topology that has 3 routers and 3 switches , one of the switches has VLans created on , when I setup one of the routers as a Dhcp server I face a problem that I couldn't assign IPs for PCs that belongs to another vlans than a defualt vlan (vlan 1) , although I create sub interfaces and assign their default gateway IP.

so , am I missing something here ?


1 Answer 1


You can use a single DHCP server to serve multiple VLAN, but to do so you need to setup DHCP relay.

It must be setup on each device that act as a gateway for a VLAN.

You must also set a different DHCP pool for each VLAN.

The exact steps depends on the equipment used so its difficult to give you a more precise answer.

  • well , I used a single DHCP server to multiple VLAN , and I made multiple pools too , but for DHCP relay do you mean I have to setup ( ip helper ) in each sub interface ?
    – MuSaB07
    Feb 17, 2016 at 15:41
  • exactly. On Cisco it would be "ip helper-address" where is the IP address of the DHCP server.
    – JFL
    Feb 17, 2016 at 15:43
  • thanks a lot ^^ I made mistake by setup relay on the interface not on the sub interfaces .
    – MuSaB07
    Feb 17, 2016 at 15:48

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