+ Post New Thread
Results 1 to 14 of 14
Windows Thread, Possible DHCP Problem in Technical; Hello there - I'm new to this forum so am hoping you guys can help me out of a hole!! ...
  1. #1

    Join Date
    Jun 2008
    Location
    Dorset
    Posts
    74
    Thank Post
    7
    Thanked 0 Times in 0 Posts
    Rep Power
    0

    Possible DHCP Problem

    Hello there - I'm new to this forum so am hoping you guys can help me out of a hole!!

    I've inherited a Windows 2003 Active Directory domain that has got a single DHCP server on the network, about 20 HP Switches and about three hundred client pcs. The previous IT Manager set it up with a subnet mask of 255.255.252.0 and a single scope of 10.12.12.2 - 10.12.15.44 with a lease period of 14 days.

    What happens is every 7 days or so, a number of PCs (that are all connected to the same switch) do their job and go and seek out the DHCP server to verify their address and to renew but they all lose their network connections - my helpdesk phone rings off its hook with users complaining! The other IT staff have been told that when this happens the "quick way" of fixing it is to reset the switch that all the PCs are connected to and this does fix the problem. When I check out the event logs on the affected PCs they all report issues with renewing IP addresses.

    I have not seen this problem before and I have not seen a single scope setup in this way before. What do you guys think? I think I should have at least one other DHCP server on the network for redundancy anyway. Should I have multiple scopes setup for four network segments (e.g. 10.12.12.x 10.12.13.x 10.12.14.x and 10.12.15.x) on the one server?

    Sorry for the long post but I'm stuck!!!!

  2. #2
    Whitestar's Avatar
    Join Date
    Dec 2007
    Location
    East Essex
    Posts
    37
    Thank Post
    4
    Thanked 3 Times in 3 Posts
    Rep Power
    14
    Well. That scope is Ok.
    That subnet mask allows for those host address ranges.

    The fact that you have been told that you have to reset the switch to get the clients working tells me that you should be looking at problems with the switch.

    If you can, try swapping that switch with another one and see what happens. If you find that the workstations start getting addresses and the other ones dont, you know the problem is the switch.

  3. #3

    FN-GM's Avatar
    Join Date
    Jun 2007
    Location
    UK
    Posts
    16,054
    Thank Post
    888
    Thanked 1,729 Times in 1,492 Posts
    Blog Entries
    12
    Rep Power
    454
    I agree it looks like a hardware problem. Does it happen to the same computers or random ones.
    We had something similar once when the onboard network card mac address where the same as other computers on the network.

  4. #4
    joe90bass's Avatar
    Join Date
    Oct 2007
    Location
    S Wales
    Posts
    1,352
    Thank Post
    325
    Thanked 107 Times in 96 Posts
    Rep Power
    51
    Yep, I'd start with the switch. What switch is it? It may be a known issue - Have you looked for a firmware update? Or it could be just plain hardware failure.......

  5. #5

    Michael's Avatar
    Join Date
    Dec 2005
    Location
    Birmingham
    Posts
    9,262
    Thank Post
    242
    Thanked 1,572 Times in 1,252 Posts
    Rep Power
    340
    I agree it looks like a hardware problem. I'd also check that nothing else is using DHCP's ports 67 and 68 on the network.

  6. #6

    Join Date
    Jun 2008
    Location
    Dorset
    Posts
    74
    Thank Post
    7
    Thanked 0 Times in 0 Posts
    Rep Power
    0
    Thanks for the quick reply Whitestar.

    The reason I thought it might be DHCP server related is I have a number of switches and this problem has happened on quite a few of them. When I check the event logs on the switches there is nothing recorded - they just report system up time (expect of course when the switch is reset!) In the past we have even had the switch management software open when the "issue" occurs and nothing is reported in the logs.

    The client PCs all record DHCP problems - and they all occur at 50% through the lease period - it just seemed to much of a coincidence that the switch goes down when the client are trying to renew?

  7. #7
    Whitestar's Avatar
    Join Date
    Dec 2007
    Location
    East Essex
    Posts
    37
    Thank Post
    4
    Thanked 3 Times in 3 Posts
    Rep Power
    14
    Try this.

    Turn off all the affected machines but one. Then manually force a DHCP renew.

    Sounds like the switch might be stopping what it thinks is a broadcast storm.

  8. #8

    Join Date
    Jun 2008
    Location
    Dorset
    Posts
    74
    Thank Post
    7
    Thanked 0 Times in 0 Posts
    Rep Power
    0
    Ok Whitestar - I'll give it a whirl tomorrow.

    Thanks for your help so far. Any ideas what I should do if it works / fails?

  9. #9
    mrtechsystems's Avatar
    Join Date
    Jun 2005
    Location
    Yorkshire
    Posts
    424
    Thank Post
    99
    Thanked 22 Times in 22 Posts
    Rep Power
    25
    Also what the is make and model of the switch

    Might be able to shed some light on it

  10. #10

    Michael's Avatar
    Join Date
    Dec 2005
    Location
    Birmingham
    Posts
    9,262
    Thank Post
    242
    Thanked 1,572 Times in 1,252 Posts
    Rep Power
    340
    Sounds like the switch might be stopping what it thinks is a broadcast storm.
    You might be onto something there, but I've never known a switch to treat DHCP requests as a broadcast storm. It's probably more likely one of the machines has a faulty network adapter and is creating the broadcast storm.

    I've seen it happen before on HP switches and all LEDs are on permanently.

  11. #11

    Join Date
    Jun 2008
    Location
    Dorset
    Posts
    74
    Thank Post
    7
    Thanked 0 Times in 0 Posts
    Rep Power
    0
    Morning all.

    The switches are all HPs - 2600's, 2800's and 5300XL's. Thanks for your help with this guys - I'm dreading the next DHCP refresh as I'm sure the same thing is gonna happen again!

  12. #12

    Geoff's Avatar
    Join Date
    Jun 2005
    Location
    Fylde, Lancs, UK.
    Posts
    11,804
    Thank Post
    110
    Thanked 583 Times in 504 Posts
    Blog Entries
    1
    Rep Power
    224
    Does your DHCP scavenging interval match your extended lease time of 14 days? As the default is 7....

  13. #13

    Join Date
    Jun 2008
    Location
    Dorset
    Posts
    74
    Thank Post
    7
    Thanked 0 Times in 0 Posts
    Rep Power
    0
    Hi Geoff.

    Not sure what the DHCP scavenging is set to and I can not remember how to find out!!

    DNS is setup to scavenge stale resource records every 7 days.

  14. #14

    Geoff's Avatar
    Join Date
    Jun 2005
    Location
    Fylde, Lancs, UK.
    Posts
    11,804
    Thank Post
    110
    Thanked 583 Times in 504 Posts
    Blog Entries
    1
    Rep Power
    224
    Sorry I meant DNS scavenging. You must set your scavenging to be the same length of time as your leases otherwise scavenging will remove DNS records to machines when they are still active and in use.

SHARE:
+ Post New Thread

Similar Threads

  1. DHCP Problem
    By dezt in forum Wireless Networks
    Replies: 20
    Last Post: 11th March 2009, 10:18 AM
  2. MAC OSX NOT GETTING IP FROM DHCP
    By thegrassisgreener in forum Mac
    Replies: 4
    Last Post: 18th January 2008, 08:50 AM
  3. The Strangest DHCP Problem?
    By tmcd35 in forum Wireless Networks
    Replies: 4
    Last Post: 9th October 2007, 12:02 PM
  4. DHCP problem across wireless since scope change
    By NetworkGeezer in forum Wireless Networks
    Replies: 2
    Last Post: 19th April 2007, 04:01 PM
  5. DHCP problem HELP!!!!
    By wesleyw in forum Windows
    Replies: 5
    Last Post: 27th July 2006, 02:33 PM

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •