Solved

dhcp, router problem

Posted on 2011-02-23
8
408 Views
Last Modified: 2012-05-11
Managers,
using a W2K3 dhcp server delivering network data for a vlan. Since some days a couple of W'XP and W7 clients won't get settings from the dhcp server anymore. On the dhcp server, such clients produce a NACK with e.g. an ip 192.x.x.x. Connecting the client to another line, i.e. another connection on the router, settings may be delivered from the dhcp server. Setting the client then back to the troublesome line and deleting the lease, again no settings are deliverd by the dhcp server. Any idea, wether it is a problem of the router or the dhcp server and how to solve it?
TIA
0
Comment
Question by:GeologyETH
  • 4
  • 3
8 Comments
 
LVL 5

Expert Comment

by:shadowmantx
ID: 34963498
Check your workstations if the DHCP Client is running and is set to automatic.
0
 
LVL 5

Expert Comment

by:rdhoore108
ID: 34967726
One thing I would try is assign a static IP address on a problematic client, and see if you have ethernet functionality then. If not, you have a network problem (wiring or bad router port/ports). If it does work, you have a DHCP problem.

I do not know the details of your network (are you reaching remote sites?), your rules on your router, or where your DHCP server is located, so the above suggestion may or may not be useful.
0
 

Author Comment

by:GeologyETH
ID: 34968909
The problem started in a sudden, i.e. the clients are set to get the network settings via dhcp server. Moving a client with working network settings from the dhcp to a "troublesome" network line, the client still works. Disabling and reactivating the network on the client  leads to a RENEW of the lease on the dhcp server.
Now, deleting the lease of this client on the dhcp server, deactivating and reactiving the network connection on the client (remaining this client on the "troublesome" network line) , brings network setting to the client, e.g. 192.168.1.33, 255.255.255.0, 192.161.1.1 gateway, dhcp and dns). Nothing to see in the dhcp server's log.
Connecting this client then to a network line on which the dhcp server delivers settings to clients, The schp server's log shows NACK 192.168.1.33, ASSIGN 82.x.x.x immediately.

All network lines are configures to the same VLAN. But on some network lines, i.e. either routers or ports on a router doesn't give access to the dhcp server. What could be the problem?

Thanks in advance.
0
Efficient way to get backups off site to Azure

This user guide provides instructions on how to deploy and configure both a StoneFly Scale Out NAS Enterprise Cloud Drive virtual machine and Veeam Cloud Connect in the Microsoft Azure Cloud.

 
LVL 5

Accepted Solution

by:
rdhoore108 earned 500 total points
ID: 34969029
Is it possible that you suddenly have two dhcp servers on your network? Maybe your router's DHCP server has been enabled, or something else that was installed recently?
0
 

Author Comment

by:GeologyETH
ID: 34969295
I have no access to the routers. Can I find dhcp servers in the network with a tool?
0
 
LVL 5

Expert Comment

by:rdhoore108
ID: 34969703
When a client needs an IP address, it sends a broadcast for a dhcp server. So, if you have more than one, there is no way to predict what will happen. Also, routers can be set to forward dhcp packets, which complicates things even more.

How many pc's do you have on your network? Are they all on one site? When you say router, is that only one router, or are there also one or more network switches inbetween?
0
 

Author Comment

by:GeologyETH
ID: 34971194
It was an unauthorized WLAN router with default settings in the network. I found it with the tool dhcploc support tool for W'XP. Since unmanaged I could logon remotely and disable the dhcp server. Now everything is running fine again.
0
 
LVL 5

Expert Comment

by:rdhoore108
ID: 34971565
I'm glad you found the culprit. I didn't know about dhcploc. It seems very useful indeed. If only it could also tell who installed it, or in which office, it would make it even more useful ;-)
0

Featured Post

Courses: Start Training Online With Pros, Today

Brush up on the basics or master the advanced techniques required to earn essential industry certifications, with Courses. Enroll in a course and start learning today. Training topics range from Android App Dev to the Xen Virtualization Platform.

Question has a verified solution.

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

Suggested Solutions

It happens many times that access list (ACL) have to be applied to outgoing router interface in order to limit some traffic.This article is about how to test ACL from the router which is not very intuitive for everyone. Below scenario shows simple s…
I recently attended Cisco Live! in Las Vegas, a conference that boasted over 28,000 techies in attendance, and a week of hands-on learning hosted by a solid partner with which Concerto goes to market.  Every year, Cisco displays cutting-edge technol…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

813 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

Need Help in Real-Time?

Connect with top rated Experts

11 Experts available now in Live!

Get 1:1 Help Now