Question

HELP! DHCP not assigning IP addresses

Asked by: Techno-Man-uk

Hi,
This morning people can not log into the network, I have checked the DHCP and it's not assigning IP addresess, I have got people back onto the network by going round and manually putting IP addresses in which is ok for now but how can I get the DHCP to start giving them out again, when users try and log in they get a DHCP can not be reached message, I can ping it fine and all looks ok.

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Asked On
2009-08-10 at 02:14:49ID24639332
Topics

Dynamic Host Configuration Protocol (DHCP)

,

TCP/IP

Participating Experts
3
Points
500
Comments
14

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Answers

 

by: gtworekPosted on 2009-08-10 at 02:18:39ID: 25058217

are there IPs available in the pool?
did you restart DHCP server service?
Is DHCP server listening on interface you use for communication?

 

by: VanikczPosted on 2009-08-10 at 02:22:57ID: 25058233

What OS is on server? Are you seeing some errors in log? What do you install on server in time when th DHCP stops assigning addresses?

 

by: Techno-Man-ukPosted on 2009-08-10 at 02:28:03ID: 25058263

Hi yes there are IP's available, have restarted the DHCP service and no luck.
It's running on Windows Server 2003, there don't seem to be any errors, have not made any recent installations.

 

by: gtworekPosted on 2009-08-10 at 02:29:53ID: 25058268

do you use firewall? Maybe you have blocked 67-68/UDP ?

 

by: Techno-Man-ukPosted on 2009-08-10 at 03:02:03ID: 25058400

Hi,
Yes we have a firewall but this has never happened before and some users have been able to log in ok but most have not got an IP address and I haven't made any chnages on the FW.

 

by: gtworekPosted on 2009-08-10 at 03:03:18ID: 25058406

Try to disable it during resolving the issue. Just to be sure...

 

by: Techno-Man-ukPosted on 2009-08-10 at 03:19:36ID: 25058482

ok done that what else can I do to get the DHCP to give out IP's again?

 

by: gtworekPosted on 2009-08-10 at 03:23:44ID: 25058504

You may also sniff the network (i.e. using network monitor) to detect request packet are reaching server and if it responds. But this is very low level action and maybe anyone can suggest something easier...

 

by: Techno-Man-ukPosted on 2009-08-10 at 03:30:45ID: 25058543

ok have just checked the DHCP lease time and its set to 4 hours?

 

by: gtworekPosted on 2009-08-10 at 03:32:32ID: 25058553

It's short but acceptable. After 2h your clients should as DCHP server for renewal and everything should be ok.

 

by: wiscomPosted on 2009-08-10 at 03:52:37ID: 25058640

Hi,

This symptom is looking like what spanning-tree is doing on the access ports. Because spaning-tree gives the switchports after 30 second free (forwarding mode) the DHCP of the client will fail.....
With spanning trre portfast you will enable the ports directly ... (as you maybe know) ...

Which switches you have installed ?

Are you sure spanning tree is ok, are there switches rebooted without save the config whitin the last 24 hours ?

Is something changed in the network within the last 24 hours ?

Did you reboot the switches (if still possible) ?

A/

 

by: Techno-Man-ukPosted on 2009-08-10 at 08:44:52ID: 25060999

Hi it's defiantely a problem with one of the switches I have 2 edimax switches and one of the problem PC's I have I connected this up to a netgear switch and could log in fine, going to reboot the switches after work and see.

 

by: VanikczPosted on 2009-08-11 at 05:34:17ID: 25068222

I have some web-managed edimax switch with 4 fiberports that completely freezes when you have DHCP server active in the network. Unfortunately I dont know the type of the switch but you can try to use some other switch instead of the edimax...

 

by: Techno-Man-ukPosted on 2009-08-13 at 04:08:12ID: 25086979

yeah is a fault with the Edimax switch, had to use a different one instead.
Cheers

20120131-EE-VQP-002

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