Solved

DHCP query relating to leases

Posted on 2008-10-04
7
182 Views
Last Modified: 2012-06-21
Hi

I have a query with DHCP that I was hoping someone could help me with.

Let's say I have a subnet of 192.168.10.1/24.

DHCP is configured to lease addresses from 192.168.10.10 - 192.168.10.20. The rest are static. The lease time is 7 days.

On Monday, I build 11 new machines that use up all the DHCP addresses.

I then take them offline and store them somewhere.

On Tuesday, if I place a new DHCP client enabled machine on the network, will it pick up an IP address from DHCP, or do I have to wait 6 days? Bearing in mind that the original 11 machines are offline, but still within their lease time.

Cheers
0
Comment
Question by:kam_uk
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
  • 2
  • +1
7 Comments
 
LVL 8

Expert Comment

by:Milan_Ojh
ID: 22640080
Hi i will suggest you to hav a link of below mentioned link it may help you a lot in left side your screen you will find Lease Process .

http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/cnet/cncb_dhc_fioy.mspx?mfr=true

Thanks
0
 
LVL 58

Accepted Solution

by:
tigermatt earned 200 total points
ID: 22640196
Hi there,

When DHCP leases addresses, it essentially removes those IP Addresses from the pool of available addresses which can be leased out, for the duration of the lease. Only when the lease time expires, and the client computer the lease was for has not returned to renew the lease, will the address be placed back into the pool of addresses available for leasing.

So, in your case, all the addresses from the pool have been leased for 7 days, so you would need to wait 6 days (or manually delete the leases in the DHCP console) before these leases are released and made available for other clients to make use of, again.

-tigermatt
0
 
LVL 70

Assisted Solution

by:KCTS
KCTS earned 50 total points
ID: 22640459
Yes you would, until the lease expires. the IP cannot be given to another computer.
0
The Ultimate Checklist to Optimize Your Website

Websites are getting bigger and complicated by the day. Video, images, custom fonts are all great for showcasing your product/service. But the price to pay in terms of reduced page load times and ultimately, decreased sales, can lead to some difficult decisions about what to cut.

 
LVL 3

Author Comment

by:kam_uk
ID: 22640531
Hi

Thanks...so, just to confirm, the DHCP server doesn't check to see if the original 11 machines are still connected? It will reserve their IP addresses regardless?
0
 
LVL 3

Author Comment

by:kam_uk
ID: 22640553
..and if we do intend to take the machines off the network, we should do an ip/release?
0
 
LVL 58

Expert Comment

by:tigermatt
ID: 22640619
kam_uk,

That is correct. The DHCP Server has no idea that the machines have left the network, because a machine will not automatically release an IP address before it is switched off.

You can either ipconfig /release the machine before you take it off the network, or delete the IP lease from the Address Leases section on the DHCP Server. Only when an IP is not listed in Address Leases can it then be placed back into the pool of addresses for leasing again.

Of course, the other option is just to ensure your IP pool is large enough to have plenty of surplus addresses.

-tigermatt
0
 
LVL 70

Expert Comment

by:KCTS
ID: 22640665
No DHCP does not - and cannot check that the machines are still connected, until the lease runs out, their IP addresses cannot be assigned to another machine.

Yes you could to an ipconfig /release, bit if you have a big enough pool of addresses, it does not matter

The other alternative is to reduce the lease period so that the leases become available more quickly.
0

Featured Post

[Webinar] How Hackers Steal Your Credentials

Do You Know How Hackers Steal Your Credentials? Join us and Skyport Systems to learn how hackers steal your credentials and why Active Directory must be secure to stop them. Thursday, July 13, 2017 10:00 A.M. PDT

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Issue: Unstable cursor in Windows XP and Windows runs extremely slow in that any click will bring up the Hour glass (sometimes for several seconds before giving you what you want) . Troubleshooting Process and the FINAL FIX: This issue see…
Today, still in the boom of Apple, PC's and products, nearly 50% of the computer users use Windows as graphical operating systems. If you are among those users who love windows, but are grappling to keep the system's hard drive optimized, then you s…
Two types of users will appreciate AOMEI Backupper Pro: 1 - Those with PCIe drives (and haven't found cloning software that works on them). 2 - Those who want a fast clone of their boot drive (no re-boots needed) and it can clone your drive wh…
In this video, viewers will be given step by step instructions on adjusting mouse, pointer and cursor visibility in Microsoft Windows 10. The video seeks to educate those who are struggling with the new Windows 10 Graphical User Interface. Change Cu…

707 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question