DHCP fault tolerance

**Sparky** · #1 21-Nov-2007, 10:43 PM

Just been reading the ‘Microsoft’ way to set up fault tolerance for DHCP.

Basically the recommendation is to apply the 80/20 rule to split the LAN scope between 2 servers which is fair enough. However MS also recommend that 20% of the range is on a server on a remote subnet.

This is what I don’t get, I will need a compatible router to forward the DHCP broadcasts and if I don’t then I will have to install a DHCP relay agent. So why not just put the 20% on the server instead of having a relay agent? Also surely putting 20% of the IPs on a remote subnet is also a potential problem as it may be at the other end of a VPN tunnel (which may be down) or behind a router which is not functioning correctly.

Thoughts?

**Boyce** · #2 21-Nov-2007, 10:50 PM

Sparks,

A guy i met in India was talking about this, and he said 80/20 works, remote agent doesn't!

"remember it does when you are in the exam though"!

Si

**Sparky** · #3 21-Nov-2007, 10:55 PM

Yeah, 80/20 is fair enough but if the 20 is on another subnet then there are other factors to consider such as the router forwarding the DHCP requests which you cant assume.