+ Post New Thread
Results 1 to 10 of 10
Windows Server 2012 Thread, DHCP Issue? in Technical; Hi folks, We've done two bits of work this week. Replacing our edge switches (old 3Com 100Mb switches to new ...
  1. #1
    Gongalong's Avatar
    Join Date
    Oct 2011
    Location
    United Kingdom
    Posts
    892
    Thank Post
    803
    Thanked 19 Times in 17 Posts
    Rep Power
    10

    Question DHCP Issue?

    Hi folks,

    We've done two bits of work this week. Replacing our edge switches (old 3Com 100Mb switches to new HP Gb switches) and (Windows) updating all our servers.

    Since yesterday I've noticed that DHCP is behaving peculiarly. When running a Ghost session yesterday all the clients had APIPA addresses. IPCONFIG /RENEW got a correct address. Again today I've spotted some PCs with APIPA addresses, yet other PCs are fine (perhaps because they were left long enough to get an address).

    There are a couple of errors on the DHCP server (Win 2012) re. contacting Active Directory, but there are one or two of those dating back to November as well.

    Any ideas where to start trying to troubleshoot this? Could a Windows Update have triggered this? Could it be our new edge switches? (I've logged this issue with the consultant that installed the switches)

    TIA

  2. #2
    ChrisH's Avatar
    Join Date
    Jun 2005
    Location
    East Lancs
    Posts
    5,002
    Thank Post
    120
    Thanked 282 Times in 260 Posts
    Rep Power
    108
    You should mirror the port of the client or use a lan tap and capture the traffic using Wireshark and look for time outs or rogue DHCP servers regarding the DHCP process.

  3. Thanks to ChrisH from:

    Gongalong (21st February 2014)

  4. #3
    ricki's Avatar
    Join Date
    Jul 2005
    Location
    uk
    Posts
    1,475
    Thank Post
    20
    Thanked 164 Times in 157 Posts
    Rep Power
    52
    Check to see if you have used all your dhcp addresses.

    Restart the dhcp service and release and renew a client

    You might have to reduce the lease time

    Or you might have a switch thats misbehaving. Try restarting all your switchs

    Have a look at the event log on the dhcp server and see if you are getting errors. You might need to update the driver of the nic card on the server.

    You need to sniff the traffic of the network to see if a computer has a broken nic and is arping or broadcasting too much

    Also make sure tree spanning is on on the switches just in case you have a loop

  5. Thanks to ricki from:

    Gongalong (21st February 2014)

  6. #4
    Gongalong's Avatar
    Join Date
    Oct 2011
    Location
    United Kingdom
    Posts
    892
    Thank Post
    803
    Thanked 19 Times in 17 Posts
    Rep Power
    10
    We have a scope of about 1,000 addresses, and this is half term, so it seems unlikely they're all used up. The problem seems to be that some machines are slow to get an address.

    I've rebooted the DHCP server, just in case.

    My guess is that it's the switches, as that's the other major change in the last 2-3 days.

    DHCP server log seems OK, well about as OK as servers ever are.

    The server is a VM, so uses a virtual NIC. I'll check to see if integration services have updated.

    We did have a problem with STP, so it was reduced to a compatible version with our older core switch.

  7. #5

    FN-GM's Avatar
    Join Date
    Jun 2007
    Location
    UK
    Posts
    15,938
    Thank Post
    886
    Thanked 1,693 Times in 1,472 Posts
    Blog Entries
    12
    Rep Power
    447
    The problem seems to be that some machines are slow to get an address.
    Ah ha! This is key. On your client switch port enable Port Fast. On a Cisco Switch CLI its: Spanning-tree Portfast

    I am confident when you enable that on the ports for your clients DHCP issue will be resolved.

  8. Thanks to FN-GM from:

    Gongalong (21st February 2014)

  9. #6
    Gongalong's Avatar
    Join Date
    Oct 2011
    Location
    United Kingdom
    Posts
    892
    Thank Post
    803
    Thanked 19 Times in 17 Posts
    Rep Power
    10
    Ah yes, Google turns up lots on this! I'll speak to our switch guys... thanks!

  10. #7
    Gongalong's Avatar
    Join Date
    Oct 2011
    Location
    United Kingdom
    Posts
    892
    Thank Post
    803
    Thanked 19 Times in 17 Posts
    Rep Power
    10
    (Presumably this would apply for HP switches also?)

  11. #8
    ChrisH's Avatar
    Join Date
    Jun 2005
    Location
    East Lancs
    Posts
    5,002
    Thank Post
    120
    Thanked 282 Times in 260 Posts
    Rep Power
    108
    Portfast is usually the default on HP.

  12. #9
    ChrisH's Avatar
    Join Date
    Jun 2005
    Location
    East Lancs
    Posts
    5,002
    Thank Post
    120
    Thanked 282 Times in 260 Posts
    Rep Power
    108
    Show spanning-tree should tell you what they are set to.

  13. #10
    Gongalong's Avatar
    Join Date
    Oct 2011
    Location
    United Kingdom
    Posts
    892
    Thank Post
    803
    Thanked 19 Times in 17 Posts
    Rep Power
    10
    I know that Spanning Tree caused some problems when the edge switches were installed as we didn't upgrade our core (3Com) fibre switch (it's already Gb). There was a version conflict apparently which caused ports to shutdown, so an earlier version of Spanning Tree was forced on the HP switches.

    We're relying on a thirdline consultant for this as switches are beyond my skillset.

SHARE:
+ Post New Thread

Similar Threads

  1. Windows 7 DNS/ DHCP issue
    By scholes99 in forum Windows 7
    Replies: 6
    Last Post: 12th December 2012, 02:05 PM
  2. Replies: 6
    Last Post: 13th September 2011, 03:18 PM
  3. Wireless and DHCP issues
    By Duke5A in forum Wireless Networks
    Replies: 5
    Last Post: 14th January 2011, 04:52 PM
  4. Weird IP/DHCP Issue
    By enjay in forum Wireless Networks
    Replies: 8
    Last Post: 11th May 2009, 03:44 PM
  5. DNS/DHCP Issues
    By link470 in forum Windows
    Replies: 1
    Last Post: 11th March 2008, 08:33 AM

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
  •