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DHCP for Servers?

By mtm1208 ·
I being asked to evaluate implementing DHCP for servers.... i think its not going to happen but need some meat to say no. I see from searching that industry wide most only use DHCP for clients

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Here's the problem with using DHCP assigned addresses for servers

by Big Ole Jack In reply to DHCP for Servers?

Your servers will be changing their leased IP addresses frequently or infrequently, depending on the lease duration, and will create a management nightmare unless you have DHCP integrated with DNS so that the A records are constantly updated with the new IP address when a server renews its leased address. Not only is this impractical, it creates an administrative nightmare because you have to ensure that your A resource records stale out quickly and are updated immediately. Now, taking account latency across WAN links and replication traffic, you'll be pulling your hair out because your clients will be communicating to the servers using expired IP addresses still in the local cache. You'll be forever instructing your users to run ipconfig /flushdns everytime they can't access a server. Servers should always be assigned static addresses because there is just too much uncertainty involved in allowing servers to get their IP addresses dynamicaly. Also, troubleshooting will be a nightmare because you'll never know what the current IP address of the server is unless you do an nslookup or look at the DHCP scope assignment table.

Another issue is that if your DHCP server is unavailable for whatever reason, your servers will be sending DHCP discover broadcasts and wil eventually give up, assigning themselves a non-routable APIPA address in the range of 169.254.x.x. This will work for servers on the same physical lan segment, but realize that since there is no default gateway assigned, your server to server communciation infrastructure has just gone to crap because you don't have a default route to communicate to and from the server.

A third reason is that by using static IP addresses, your LAN switches won't be overloaded by constantly having to update their ARP tables everytime a server gets a new IP address. It's bad enough the clients are keeping the switches busy with ARP table updates and convergence issues, but now the servers will add to the workload.

Simply put, it's not practical for servers because it increases the total cost of ownership and administration.

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DHCP for servers

by RFink In reply to Here's the problem with u ...

You could set up DHCP reservations for your servers.

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Yes, but what if DHCP server is down? You get APIPA nightmare

by Big Ole Jack In reply to DHCP for servers

It's just not practical to have servers get their IP addresses via DHCP.

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DHCP for Servers?

by mtm1208 In reply to Here's the problem with u ...

Big Ole,
Thanks!!! this is exactly what i needed...

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DHCP - this is a real project

by mtm1208 In reply to Here's the problem with u ...

couldn't we use DHCP to assign initial IP addresses to a server at build time, but assign them as permament?

We are trying to avoid manually keying so we can build servers anytime, day or night, and not expose us to manual intervention...

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by jayson.allen In reply to Here's the problem with u ...

There is honestly no issue with enabling DHCP on servers. Setup the service to renew addresses ever 15-30 days, and setup reservations for each server so they get assigned the same IP. As for the "if the DHCP server goes down" arguement, think of one thing....what else is going to be affected if DHCP goes down? THE CLIENTS! If your service goes down, the clients will also be exposed to the same issues and cannot connect to the server. What does a normal IT person do when their DHCP server goes down or isn't working? They fix it immediately.... LOL! I wasn't too cracked up about doing this on a network till I really put some thought into it. Makes management easier that's for sure...

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by mtm1208 In reply to WHAT?!?!?!

Thanks... havent heard anyfeed back from my document to management on this... so its dormant for now...

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Who asked you to evaluate that?

by Genera-nation In reply to DHCP for Servers?

Are you the New Guy?

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by mtm1208 In reply to Who asked you to evaluate ...

Dam, how did you know!! new to the Open systems section anyway....

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I think his managers are busting his chops with this silly project

by Big Ole Jack In reply to Who asked you to evaluate ...

because nobody I know of, at least mentally sane, would setup servers to acquire their IP addresses via DHCP. I have come across companies that are still statically assigning IP addresses to client PCs' and such places get a quick tongue lashing from me and a good smack upside the head. There should be no reason to run around and keep track of statically assigned IP addresses for client PCs' because client PCs' should be considered as commodities that can be easily swapped out and replaced. Servers on the other hand are a different story.

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