Hi All,
Here I sit, alone in our office, to change our subnet. I hardly got any sleep last night because of it. I might need some help today as this is my first attempt doing this task.
The details.
We have a DHCP scope that is 192.168.0.x and are quickly running out of address space.
Today I will change that to 192.168.x.x
One question that has been bothering me is, can I have a dhcp scope of both 192.168.0.x and 192.168.x.x on the same DHCP server?
Thanks in advance and here we go!
Take care,
5 Spice ups
How is the server going to know which pool to issue the numbers from?
Also, if you have two machines with 192.168.0.1 from the two pools then you’ll have issues, no matter the subnet mask so don’t do that.
I hope you changed the DHCP lease time to something very small, it’ll make the work so much easier.
Yes you can have multiple scopes on the same DHCP server as long as the pools don’t overlap.
Hi,
Didn’t know if you use this, but might help you… Online IP Subnet Calculator and CIDR Calculator
larsen161
(larsen161)
5
Hey Jason, as long as they are non-overlaping you can run multiple. So you don’t wat to run a single /16 network but rather divide them up how you want. For example, I’ve used a /8 network In terms of overall scope but the largest one in use is a /22 at the moment. Remember to allow for space between scopes if you ever want to expand upon them in the future without too much extra work.
So It’s not a big deal because we don’t have a lot of reservations, should I just backup and delete the scope and then create a new /16 scope and add those reservations back? I’m only looking at 10-15 reservations.
can we assume you have 254 addresses then ? so a 192.168.0.0:24 ?
if you just want to add addresses alter it to a 192.168.0.0:23 this will give you 512 address - 2 = 510 available
and if you were 192.168.0.0 / 192.168.0.254
you will now be 192.168.0.1 / 192.168.1.254
maxsec
(maxsec)
8
If you’re in ‘emergency’ mode then
-
drop the scope lease time to 8 hours or less, this can help by getting rid of ‘off site’ devices more quickly
-
move to a /23 expanding the current scope and altering the gateway to the same subnet.
Right now you’ve got some time to think about how you’re going to redesign the network in a more thoughtful manner, infrastructure to static addresses and more space for ‘user land’ equipment.
1 Spice up
Not in emergency mode. I have the weekend to pull this off as everyone is gone.
I’ve researched all of the settings on all of the devices that needs to reconfigured. I’m just a little stumped by the scope.
maxsec
(maxsec)
10
I’d still say thats emergency if you havent planned this before implementation!
You should be able to extend the subnet to a /23 and drop the lease time down. Then it’s just the static addresses you need to alter the subnet on manually.
1 Spice up
I’ve already lowered the lease time. And my initial plan for implementation was to remove the scope and replace the reservations manually. My question was simply do I have to do that to move from a /24 to /16.
Okay perhaps /23 makes more sense given our growth.
maxsec
(maxsec)
15
If you’ve got reservations then move them to static entries - say at the bottom of the /23, and redo the lease.
Planning is the key here…keep all the infrastructure off dhcp so you’ll survive when dhcp service is slow to start and the userland stuff can stay on dhcp
If you’ve got byod consider moving these to another subnet and wifi SSID
1 Spice up
Very good thanks everyone. Make reservations static. Move BYOD into it’s own subnet (already in place), go with /23 .
Thanks.
larsen161
(larsen161)
17
Here’s something that may help you in planning your network. I put this together when I started planning the networks across all our offices. Not all are included here but there should be enough to get an idea of how it all fits together.
Office Network Scopes
1 Spice up
Thanks Steve, that is very helpful.
Well I have to say, that wasn’t as hard as I thought it would be.
I moved many switches, voip, servers, and management interfaces on iSCSI storage with no issues.
The method of changing subnets via http://social.technet.microsoft.com/wiki/contents/articles/8484.how-to-easily-change-a-dhcp-s-scope-subnet.aspx worked nicely in testing and worked as well on the production network. I can’t complain. It was easy.
All I need to do now is reconfigure a couple printers and I am done.
Thanks for the recommendations everyone. I’ll do a KB on this and give back next week.
Take care,
Oh and reconfigured inside interfaces, VPN as well.