Setting up a standby DHCP server.

[tosca925]

I have set up another server with DHCP on our domain purely for redundancy. I don't want to use the 80/20 rule. I know the standby DHCP server requires manual intervention if the other DHCP server dies but this will do for me at the moment. I exported the DHCP settings using netsh DHCP server and imported them the same to the other server ok. I have a Scheduled task to run to export the DHCP settings nightly to a txt file so i can import the most up to date settings quickly if i did need to manually start the other DHCP.

My only question is and i think i am correct thinking this anyway but second opinions are always good.

I have imported the scope to the standby server, the DHCP service is running, but i have not authorised the scope yet. Can i leave it sitting like this and then just authorise as i need it in case of the the DHCP server going down, or do i need to stop the DHCP service and start it when i need?

Ihave also set the 'conflict detections attempts' to 2 as recommended my MS for a standby server.

[StewartKnight]

You should just be able to activate the scope... in theory.
However, I've found that this doesn't always work, but to unauthorise, then authorise the server and start the scope doesn't take a minute.

What is does do though, is cock up, because it tried to dish out IP addresses that are already taken, and you get lots of false positives saying that there is a clash of IP addresses.

And before Geoff jumps in to explain that DHCP shouldn't do that thanks to wonderful OFFER REQUEST LEASE & ACK ... it just does, but then again, it is Micro$hafts version of the DHCP standards!

[zag]

I always wondered about redundancy in this area as well, but it takes a few minutes to setup and configure a new dhcp server, just record your settings like scope and install it when its needed.

[tosca925]

What is does do though, is cock up, because it tried to dish out IP addresses that are already taken, and you get lots of false positives saying that there is a clash of IP addresses.

Ihave also set the 'conflict detections attempts' to 2 as recommended my MS for a standby server.

This should help with your problem you mentioned.

[Geoff]

Yes the above information is correct. Assuming your active directory replication works (DHCP lease information is stored in AD) and you have conflict detection enabled there should be no problems.

[srochford]

Why not just have 2 servers set up with non-overlapping ranges?

eg if you're using 10.0.0.0 - 10.31.255.255 as your range then split it in half. One DHCP server gives 10.0.0.0 to 10.15.255.255 and the other gives 10.16.0.1 to 10.31.255.255

You can have both servers running and they will spread the load (not much load for DHCP!) and give you redundancy. You obviously have to make changes to both servers if anything changes but it's pretty rare that DHCP settings need changing so it shouldn't be a big job.

[Geoff]

You've more or less just described the 80/20 rule. Well done.

[Heebeejeebee]

You've more or less just described the 80/20 rule. Well done.

8O

80/20 v 50/50

HBJB