Simple DHCP Networking/Router Question

hitman47 · 6 Jul 2006 at 14:57

Pretty simple networking question and scenario:

I have two computers and a wireless laptop. The two computers are manually defined to be 10.0.0.3 and 10.0.0.4 respectively. The wireless laptop is set to automatically pick up its IP address.

Now currently the router is set up as a DHCP server ranging from IPs 10.0.0.3 to 10.0.0.5 so typically the laptop picks up 10.0.0.5 . However, as I found out today, if the two computers are not turned on, when I turn on the laptop it is free to take 10.0.0.3 say, and so this causes an IP conflict when I turn on the computer manually assigned to be 10.0.0.3 .

It seems pretty common sense to me, but if I set the DHCP server to give out IPs from 10.0.0.5 to 10.0.0.5 say, would this resolve the problem? ie can the two computers still manually assign themselves their IPs even though the router is not "providing" 10.0.0.3 and 10.0.0.4 from the DHCP server?

Therefore if im correct the wireless will always only be able to pick up 10.0.0.5 from my router, effectively reserving 10.0.0.3 and 10.0.0.4 for my two computers.

Sorry about the lengthy post, but networking buffs should be able to set me straight pretty easily! Its just I cant test it now till I get home.

Thanks!

oddjob62 · 6 Jul 2006 at 15:06

You wouldn't want your DHCP scope to be 10.0.0.5 to 10.0.0.5, because once that IP is taken there won't be any more.

But you can manually set IPs outside the DHCP scope, they will work fine.

hitman47 · 6 Jul 2006 at 15:08

Excellent just what I needed to hear!
I only suggested 10.0.0.5 to 10.0.0.5 because thats all I need but indeed for the future I will increase the scope.

Thanks again

Musashi · 6 Jul 2006 at 21:46

As a general rule you never assign static ip's from your dhcp range, you are heading for trouble if you do.

BenST · 7 Jul 2006 at 11:19

Some routers allow you to assign IP's to certain MAC addresses, so you could set 10.0.0.5 to MAC XX.XX etc therefore the laptop would always be assigned the same IP. Of course the other thing to do would be to assign the laptop wit a static IP but leaving it DHCP makes it easier when you want to connect to other networks.

Also as said it's never good to assign static IP's within a DHCP range, as I found out recently with my neighbours wireless config kept knocking out my connection!

hitman47 · 7 Jul 2006 at 12:20

Musashi said:
As a general rule you never assign static ip's from your dhcp range, you are heading for trouble if you do.

Of course, it just never occurred to me that you could assign static IPs outside of the DHCP scope! All is well now.

And as splitz said, I leave my wireless laptop to automatically retrieve the IP from DHCP which makes it much easier when out and about in uni for example.

Thanks again