DHCP dish out different IP ranges per VLAN

[tj2419]

Hi

 

Is it possible to set up our DHCP so it uses different IP ranges for different wireless SSID's? We are also probably going to VLAN them off as well.

 

Basically

Guest SSID - 10.24.91.0-255

BYOD - 10.24.92.0-10.24.94.255

 

Cheers

[Techie2000]

Yes its possible - it is easier with VLANs already configured as you would have two scopes setup.

 

You will also need to ensure your wireless system allows VLAN configuration (I've only seen one or two which don't and they were old!)- if it does you can input the VLAN ID for each SSID to use.

 

On your layer 3 / router you would configure VLAN ID and Address (using the network address such as 10.24.91.254 255.255.255.0)

You would then simply create another VLAN and do the same for your BYOD using a different VLAN ID and using the network address 10.24.94.254 255.255.253.0

 

Remember to modify the subnet mask for your BYOD network, otherwise you will end up with a /24 network. - This setting will need configuring in your DHCP scope and on the router / layer 3.

[tj2419]

This setting will need configuring in your DHCP scope and on the router / layer 3.

 

Thanks. What do you mean by this sorry?

 

How do the rest of our wired computers know to ignore the .91 - .94 range?

 

Thanks

[Gaz]

How do the rest of our wired computers know to ignore the .91 - .94 range?

 

Your wired network will have a router entry on the dhcp scope which is the default gateway of that vlan.

 

Just like your BYOD and guest networks will. Thats how dhcp will be issuing IP's out to the correct network.

[sonofsanta]

Yes. Absolutely.

 

Depending on the level 3 switch you have as your core router, you need to configure your DHCP relays.

 

All this is for Comware (i.e. 3COM, HP5800/5100 switches).

 

Core config:

dhcp relay server-group 1 ip 192.168.1.1
dhcp relay server-group 1 ip 192.168.1.2

where the IPs are the addresses of your DHCP servers.

 

Then on each VLAN

interface Vlan-interface2
description Cab2 Workstations
ip address 192.168.2.1 255.255.255.0
dhcp select relay
dhcp relay server-select 1

The IP address there is the default gateway for that VLAN followed by the netmask. Description is whatever you want. The last two lines tell the switch that addresses are assigned by DHCP, and to forward DHCP requests to relay server group 1 - which you set up above.

 

Then on your DHCP servers, just set up the ranges - e.g. Cab2 VLAN, start 192.168.2.10, end 192.168.2.255, 255.255.255.0 mask, default gateway 192.168.2.1, and any other options as required. When the switch passes the DHCP request along, the server will know what range it came from and assign an IP as relevant. I normally start my DHCP ranges at .10 so there's a handful of addresses available for static assignments.