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What is the best way to assign IPs in your opinion?

I've got ~100 PCs, some servers and see three ways to assign IPs:

  1. Static IPs for every PC/server
  2. Static IP reservation by MAC-address in DHCP
  3. Dynamic IPs via DHCP.

Of course, you can combine them, i.e. dynamic for PCs, static for servers.

But, again, what is the best way? How do you do that?

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2 Answers

up vote 14 down vote

We go static for servers, dynamic for everything else.

You want to go DHCP everywhere it's practical. In fact, the only time you want to go static is a) AD DNS servers b) behind a port forward - and both of these can be sorted with a DHCP lease if you want.

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I'm paranoid enough to set static on a few more servers, but in genereal: What he said. :) – Gomibushi Apr 30 '10 at 10:48
+1. I would also strongly recommend splitting up the network right now in a DMZ and an Internal network, create separate subnets putting a firewall between, so you get the standard network layout. – pehrs Apr 30 '10 at 11:15
up vote 3 down vote

You definitely need some static IPs (for your DHCP server for example), but you can do static allocation via DHCP using MAC addresses for servers. The benefit of that is that you have all your IP address configuration in one place - but you create a dependency on your DHCP server.

Say you have a power outage, and for some reason your DHCP server is the last to come back up on recovery - you then end up with none of your servers having any IP address which wouldn't have happened if they were static. Some of them will "acquire" 169.254.x.x type addresses and may be able to talk to each other but not the outside world - others will not get anything. You turn up in the morning after this has happened, and you have a lot of work to do!

So I think static for servers is good (keep decent records!), and dynamic via DHCP for clients.

Maybe for printers and other non critical network devices, assignment by MAC address is worthwhile, since the interface for setting their IP addresses may be a bit obscure.

You'd have to get pretty large for the admin benefits of assigning everything via DHCP to be of particular benefit IMHO.

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So to bypass this IP disaster, DHCP server should be on dedicated (not vm) server to boot up first. But I get your idea. – user41893 Apr 30 '10 at 12:27
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"...keep decent records!..." Absolutely! – jl. May 5 '10 at 17:17
I don't think you would want your DHCP server on a VM, for the reasons you state. Many higher end switches (and some lower) can do DHCP, and depending on your requirements, this might be enough, without having to dedicate a server to the task. – dunxd May 6 '10 at 8:29
@dunxd: try configuring some DHCP reservations on a Cisco device, and you'll begin crying... – Massimo May 6 '10 at 8:40
@Massimo - it isn't all that hard - you can do it via the console, or use SDM to set the bindings via a GUI, or even use the web front end. On a small network with the right switch/router it is quite viable in my opinion. We don't do it here, but there are times I wish we did... – dunxd May 6 '10 at 8:58
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