• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 107
  • Last Modified:

On Server 2008 R2 - Expand /24 to /16 Netmask

Client has small network, 1 AD/DHCP/DNS Box - Server 2008 R2 Enterprise with one 192.168.1.x/24 network. Has been expanding throughout years with computers, ip phones and ip cameras and have run out of ip addresses. What is the easiest way to acquire more IPs? I assume by changing subnet mask to /16? Is there a way to do this with very little downtime to network? Can I and if so, how, export my current dhcp scope and reservations, modify the file to /16 then import back? Thanks for help.
0
xav1963
Asked:
xav1963
  • 4
  • 3
  • 2
1 Solution
 
RantCanSr. Systems AdministratorCommented:
Broad steps:
1. Change DHCP Lease time to 15 minutes;
2. Create new scope with changed Netmask (recommend going to 192.168.1.x /22 which gives you 192.168.0.x, 1.x, 2.x, 3.x  as well)
3. Activate new scope
4. Deactivate old scope
windows clients should renew with new scope.

Caveats:If you are not using VLANS, you must be cautious because this is still a single collision domain, and you might increase your broadcast traffic an intolerable amount, based on your description.  I recommend setting a VLAN for IP phones (so you may apply QoS), as well as one for servers, one for cameras, reserving  a single VLAN for workstation traffic.
0
 
xav1963Author Commented:
understand ... so there is no need to create a superscope?
0
 
RantCanSr. Systems AdministratorCommented:
Not if you are moving to VLANs, which is recommended. I would try to keep the individual VLANs as flat as possible; superscopes don't add any advantage if you have a properly VLAN segmented routing network. Is your infrastructure capable of properly routing VLAN traffic. If the answer is yes, no superscopes. This article explains in technical details why superscopes are generally useless in a properly switched network.  http://robertparten.com/dhcp-multiple-scopes-vs-superscopes/
0
Network Scalability - Handle Complex Environments

Monitor your entire network from a single platform. Free 30 Day Trial Now!

 
xav1963Author Commented:
understand ... just need a few more IPs ... will investigate network and tackle vlans later ...
tried your instructions and getting error due to overlapping network, I would have to delete old scope first, losing existing leases or reservations if possible ...
I tried this link but also am getting errors ... https://www.petenetlive.com/KB/Article/0001177

Still back at square one ... need to create new scope of 192.168.1.0/22 and save existing leases and reservations at same time ....
0
 
RantCanSr. Systems AdministratorCommented:
DHCP protocol will attempt to renew it's lease halfway through it's current lease. With this in mind, if you set your lease to 4 hours, you'll have two hours to make the changes. If you do it on the weekend, and test out, then you have enough time to perform the functions.  The linked article seems straightforward.  What errors are you getting using the dump/edit/delete/import steps?
0
 
QlemoBatchelor, Developer and EE Topic AdvisorCommented:
RantCan, changing the DHCP lease time does not help if machines do not get restarted or forced to renew DHCP leases. If machines are running 24/7, they will only ask after half of the original lease time for rconfiirmation of their IP.
0
 
RantCanSr. Systems AdministratorCommented:
Which is why I recommended to SHORTEN the lease time prior to undertaking this config change.
0
 
QlemoBatchelor, Developer and EE Topic AdvisorCommented:
Imagine you have a lease time of 14 days - which is not uncommon.Then you cannot get this work before a week has passed ;-).
0
 
xav1963Author Commented:
thanks for answering question ... think I asked question incorrectly ... will try again later..
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Cloud Class® Course: Microsoft Azure 2017

Azure has a changed a lot since it was originally introduce by adding new services and features. Do you know everything you need to about Azure? This course will teach you about the Azure App Service, monitoring and application insights, DevOps, and Team Services.

  • 4
  • 3
  • 2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now