Dual (backup DHCP) Servers, one goes down, 169.x address as result

[markm75]

Here is my domain config: Two DCs, a few member servers.. a GC is set on both DCs. Both of these DCs act as DNS/DHCP servers, providing fault tolerance if one server is down/off.

Earlier today we had one of them offline.

A brand new workstation was brought out of its box today, connected to the wall.

It failed to find an IP address.. went into 169.x low connectivity mode.

Similarly, existing workstations (i'm assuming ones who had ip addresses from the secondary, down, DHCP server) that were working fine, if repaired the connection or logged off and back on.. could not then attain an ip address.

Shouldnt this fault tolerant situation still allow for the workstations to retrieve an IP address from the other DHPC, if the other one goes down?

I really was at a loss as to why the redundancy wasnt working (no error logs either)...

Thanks for any help.

 

[nsantin]

How have you setup your scopes? Did you make it a Superscope?

 

[itsp1965]

Usually when you setup DHCP "fault tolerance" you would balance your DHCP scopes between two servers. Ex) x.x.x.1 to x.x.x.100 would be one server and x.x.x.101 to x.x.x.254 on another (of course this depends on the type of addressing and subnet mask you are using).
- You haven't indicated how you have setup you fault tolerant scenario for DHCP. Are they using the same scopes on both servers (this won't work)
- Are the DHCP servers connected to different subnets? How are they setup on the network? do you have VLANs or are all your servers connected to the same segment?

You will need to provide more detail on your environment.

 

[markm75]

Sorry for the limitted details before.

Both servers are on the same subnet (the only one).. They arent setup in a true 80/20 setup, more like what you mentioned.. up to say .150 on one then .151 to .253 on the other etc.

They are both authorized.

I kinda doubt that the first one (the one that was still running when the other was down) had run out of ip addresses too.

I didnt think to check on that when it occurred.

 

[itsp1965]

Do you have a server running IAS (RRAS) this would take a chunk of your IP addresses from DHCP for this purpose.

 

[markm75]

I do have RAS going for a seldom used "backdoor" vpn ability, however, only about 1 person per day would be using it (installed on a different server).. I have it set to use DHCP to give out the addresses...

 

[itsp1965]

Well be aware that a RAS server grabs IPs from a DHCP server in chunks of 10. You may want to check your DHCP servers to ensure that all IP addresses have not already been used up in this case