I would be very grateful if anyone could offer any advice on this issue.

I have two different Drayteks 2820/2860 with their own connection to the internet and various Pc's connected to them.

I have configured them so each network has their own subnet and connected the Drayteks inorder for the PC's to access things on the other subnet but ideally use their own internet connection. The problem is that some PC's/Devices are now getting IP Addresses from the different router they are connected to. Which then obviously means they end up on a different subnet and using the wrong internet connection. Not ideal.

I was wondering whether the only option was maybe to block UDP(DHCP) requests between the routers inorder to stop the PCs getting onto the wrong subnet?. Am I missing something obvious?

Edit: Added picture if my explanation wasn't very clear.

If you've linked the Drayteks via their switches, they will both be in the same layer 2 network so the DHCP broadcasts will reach both routers and the first one to respond will get the client.

You could create a VLAN on one of the routers, so that the other router will then be in a separate Layer 2 network, then enable inter-vlan routing between them.

Doing it this way, you can also choose to allow one of the routers to do the DHCP for both subnets, or keep them both doing their own.

Thanks Steve, much appriciated.

The 2820 doesn't do inter-vlan routing so will try this config on the 2860.

Let me know how you get on.

You will need a static route on the 2820 telling it that the other network is via the IP you give the 2860 in the VLAN.