Backup DHCP server possible? 2

[1666]

Hi, our PDC is running a DHCP scope for our company, is it possible to have a Backup DHCP server on our BDC encase the PDC fails one day? Also can it be the same scope?

Andy

 

[GlenJohnson]

It sounds like you're running NT, not W2K. Correct? Glen A. Johnson
Johnson Computer Consulting
MCP W2K
glen@johnsoncomputers.us

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[1666]

I do apologize, your correct it is a NT 4.0 domain...

 

[SgtB]

If you're PDC fails, you'll have bigger probs than you're DHCP server!
j/k

Unfortunately, I don't think DHCP lends itself to failover/backup type solutions. The best thing I can offer in the way of advice is to have a second DHCP server with all the same settings up and running w/o the scope being active. In case the other fails, you can activate the scope of the backup. This may cause some issues with leases and such, but a release/renew would fix that problem.
If anyone has any other ideas, I'd love to hear them too.
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[Whoheard]

If you have enough space in the IP address range, then add a second scope with address not in the first scope; i.e. Scope 1.) 192.168.10.33-64, Scope 2.) 192.168.10.65-90.

Do you have the whole subnet on DHCP or just part of it?

Bob

 

[Whoheard]

Sorry, I forgot to add...
I am assuming that you want the DHCP for client accecss only. You should never put servers on DHCP--this is trouble waiting to happen.

Bob

 

[GlenJohnson]

Scope 1.) 192.168.10.33-64, Scope 2.) 192.168.10.65-90.

Make sure you have a superscope with each other left out. Good luck. Glen A. Johnson
Johnson Computer Consulting
MCP W2K
glen@johnsoncomputers.us

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

"It's not what you look at that
matters, it's what you see."
Henry David Thoreau (1817-1862); US essayist, poet.

 

[SgtB]

Do how does having two scopes help if the machine completely dies? Please elaborate a little. If the machine is dead its dead....two scopes or not.
(not being a smartass, just wondering) ________________________________________
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[Whoheard]

The original question was, can you have a Backup DHCP server on the BDC? IF the PDC fails in any way, the BDC will takeover and so the BDC DHCP service will become sole provider of IP's.

Actually there is sort of a red herring here. There is no backup DHCP server. The DHCP service running on the BDC is always going to give out IP's to users, even if the PDC is up and running. Once it is set up and turned on it goes to work. In the instance of a failed PDC, it just keeps on giving out addresses as if nothing has happened.

It is a good idea/practice to have two DHCP servers when using DHCP; both capable of serving most, if not all, of the network. This helps with attaining the five 9's goal.

The big misunderstanding comes from Admins trying to run two DHCP servers with the same scope. This increases the chances of having duplicate IP's. The scopes need to be different.

For example. You have Class C address. You can have a max of 254 IP's within that class; but you only have 100 users. You can have the PDC DHCP server giving out 100 addresses--X.X.X.51 - X.X.X.150; and the BDC giving out a 100 addresses--X.X.X.151 - X.X.X.250. There is no overlap, no danger of duplicate IP's and each server is capable of handling the whole network if need be. This can also be adjusted based on admin/user needs.

A proper IP addressing scheme is paramount to the success of the network. There are many areas which can get a person into trouble and cause lingering problems.

There are many references out there on DHCP, and MS has a number of papers on this subject on their website. I would encourage anyone to read more on the subject before implementing this service.

Hope this helps


Bob

 

[SgtB]

Hey great explanation. I must have gotten a little confused somewhere in the thread!
I never thought of running two DHCP's with two scopes for backup. Quite an explanation on the subject too. I appreciate it! ________________________________________
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[Whoheard]

Just remember. Two servers running DHCP service with one scope on each server. A scope is a portion of addresses from within the full ip address range. MS DHCP server will not let you configure more than one scope within an IP subnet.

Thanks for the feedback.

bob