[Wolves] Newbie Networking Question if you don't mind

[Wayne Morris]

Hi guys,

Long time no bother with question ;-)

This may well be a question with a simple answer, or open a can of worms.

I have a property that we want no down time for internet access, so 
currently have a Virgin internet
box as well as a BT connection.
If both services are up, VOIP phones are through one connection and 
computers all through the other, then if one fails we just
shift a patch lead from one to the other to run all services through one 
router. DHCP done by each router.

So, clearly to automate this I need a switch between both incoming 
routers and the two subnets.
Guessing? This would immediatley screw up dhcp as only need one one a 
working network, but if that connection failed, would lose DHCP.
Would the right Switch be used instead for the DHCP?
We also have an incoming port forward to security cameras to watch 
remotely, would the right switch be programmable for this?

Any answers or pointers to a simple tutorial?

Thanks

Wayne