DHCP not working

[TheMikeh]

Hey,

Basically we have a small business network consisting of 6x servers, 30 client machines and 5 managed POE switch's. We then have an endian os firewall on a server which manages routing etc. Now DHCP has and always was enabled on our primary domain controller and worked fine, however all our machines are static IP'd except the laptops.

For the past week the laptops have been failing to get a valid IP address and just shows as being on an 'unidentified network'. Now Ive got a program called DHCP Find and when run on the laptop it shows a packet being recieved stating the correct DHCP server and a valid IP address but it doesn;'t seem to go any further.

Ive checked that the DHCP scope is correct, with the correct DNS, WINS and ROUTER values on the scope, ive even tried a fixed lease using one of the laptops MAC address's and still nothing.

Does anyone have any ideas? all the laptops are Win Vista SP1 machines, the DHCP is on our primary domain controller which is 32bit Win 2003. I have even tried disabling the DHCP on the domain controller and turning on the DHCP on the firewall and it still does the same.

Any ideas? help!

Thanks
Mike

 

[SimonDavies]

First question to ask is.. what changed in the last week. Was anything new installed onto the network? was anything changed on the switches?

Usually if something was working and then fails it's down to a change that's occurred on the network.

First place I would look would be on the switches to check that the IPHelper address is still configured correctly.
Next I would check to see what happens if you plug a laptop onto the same vlan that the server is located on.

Next I would be checking the event logs on the server and laptops to see what it says when it trys to obtain the lease.


Simon

The real world is not about exam scores, it's about ability.

 

[TheMikeh]

Hi,

Ive checked all our switch's and they have a DHCP Relay option which I have tried turned on and turned off and either way it had the same effect.

If I plug the cable into a machine, the system says 'identifying' and then after a few minutes it then goes to 'unidentified network' and is sitting on an IP address of 169.254.213.255 with 0.0.0.0 as the gateway. In regards to network changes, nothing at all as been changed, the room is even locked so a bit unsure why its playing up now, there again the DHCP might of been down for ages since 99% of machines are static and then 99% of those that arent connect via wireless (different network).

The lan is very simple, there is no vlan's, just simple cables straight back to 4x managed switch's, these in turn are then connected to a single gigabit switch which holds all the servers.

Im in the process now of having a quick check through the log files, anything in particular that I should be keeping an eye on?

 

[SimonDavies]

The 169.254 address is called APIPA, it means that it can't contact a DHCP server and has allocated itself the IP address you see there (it's an MS Windows feature).

I would definitely start looking at log files.

Simon

The real world is not about exam scores, it's about ability.

 

[TechyMcSe2k]

I know you have Windows 2003 DHCP, but read this and I'll research further:

http://support.microsoft.com/kb/928233

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[TechyMcSe2k]

Also, make sure the Vista Firewall or any other firewall software is turned off and see if that resolves issue. also, if you delete the NIC and reinstall it, does the issue go away?

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[TheMikeh]

In response to the very last post, I cant see how firewall on the machine and deleting/reinstalling the nic will work because its all laptops with the problem (5x vista, 1x winxp pro). Will give all suggestions a go and Ill read that link, thanks

 

[TechyMcSe2k]

QUOTE:
all the laptops are Win Vista SP1 machines

just going on the information given.

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[TheMikeh]

Yes sorry just realised that there is a single XP laptop that is also doing it, but even then it seems a bit odd that every laptop would suddenly develop this problem? I will try anyway though just to rule it out.

 

[TechyMcSe2k]

if you put a static on the laptops, do they communicate with the network?

Anything in the laptop logs?

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[NetworkTek]

What is your wireless infrastructure?? Just wondering and this is something simple if it has dhcp turned on and causing a conflict because you have to two dhcp servers on the same network. Just a thought

Network+ Inet+ MCP

 

[TheMikeh]

The wireless is a seperate network all together, its purely internet access via 2 access points, its seperate from the wired network due to security. I have a program called DHCP find and when you click the button the right DHCP server returns a valid IP address, its just the laptops pick it up as an un-identified network, its odd.

 

[TheMikeh]

And yes, when set to static IP's all machines connect and run flawlessly, my laptop was static hence why I never noticed it and the other users saw cable didnt work and just flicked over to the net as they only really need internet ...

 

[TechyMcSe2k]

Do the Access points have a proper gateway address?

wired network--->Access Points--->Laptop (asking for IP)
LAN w/DHCP forwarding
wireless
requests
to wired network

I would say the issue is with your access points.

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[TheMikeh]

No no, let me explain ...

The wireless network is 100% independent, its literally a ADSL2 modem and 2 access points used to give internet access to our guests/visitors.

Our main network has no wireless at all and is fully cabled, virtually every device is running from static IP's and those which don't (such as the laptops) are failing to receive a DHCP address. If I connect a machine to the 'wireless' network via cable and/or wireless the DHCP works fine on that network thus making me assume its a problem with the other network rather than a problem on the laptops.

If using a DHCP 'finding' tool, on the laptop they send a DHCP packet request out, and a response is returned immediately and is all correct but no machines seem to 'accept' the address. Could it be possible there is another device on the network that is also issuing DHCP requests?

 

[TechyMcSe2k]

Quote:
DHCP might of been down for ages since 99% of machines are static

There has to be an issue with your DHCP setup. If most all of the machines are static, then that explains why the work.

Post your DHCP scope options and we see what may be missing.

Standard/basic ones are
003 Router = Gateway
006 DNS Server = DNS Server IPs
015 DNS Domain Name = yourdomain.com
044 WINS/NBNS Servers = WIN Server IP
046 WINS/NBT Node Type = 0x8


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[TheMikeh]

Standard/basic ones are
003 Router = 10.10.254.1
006 DNS Server = 10.10.254.1
015 DNS Domain Name = chelco.local
044 WINS/NBNS Servers = 10.10.1.2
046 WINS/NBT Node Type = 10.10.1.2

And its set to distrube IP's from 10.10.100.1 to 10.10.100.200

 

[TechyMcSe2k]

046 WINS/NBT Node Type = 10.10.1.2
How is this an IP? prob. typo

Router IP 10.10.254.1.....is this the Windows 2003 server or the endio Firewall?
DNS Server 10.10.254.1...same question

The IP range is 10.10.100.x (DHCP) Network is (10.10.254.x) What subnet are you using? With a network of only 6 servers and 30 clients, I was wondering why such a large IP pool (network from 10.10.1.x-10.10.254.x)?
Maybe a DHCP IP range in the 10.10.254.x would be a better solution so that there is no effort in reaching the DNS and Gateway addresses.

I am starting to believe this is a network configuration issue now.

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[TheMikeh]

10.10.254.1 = endian firewall
10.10.1.2 = primary domain controller

Services IP's sit on 10.10.1.x
DHCP IP's sit in 10.10.100.x
Static IP's sit in 10.10.101.x
Printers IP's sit in 10.10.102.x
Fax Systems sit on 10.10.103.x

Avaya Phone system is 10.10.2.2
Avaya Phones are 10.10.2.x

Subnet is 255.255.0.0 ... this was exactly how it was when I started working here, its always worked and thus ive never found a need to change it around due to the large levels of configuration involved.

 

[TechyMcSe2k]

006 DNS Server = 10.10.254.1

is the DNS hosted on the Win 2K3 machine? Which is at IP 10.10.1.2 which holds the PDC Emulator role for your AD domain? Your are running Windows 2003 AD, since you stated Primary Domain Controller is on W2K3 server, correct? DNS should be AD integrated on this server. Point clients at that server.

Change the 006 Scope option to represent the proper DNS of 10.10.1.2.

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