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DHCP Server Not responding to DHCP Discover

Posted on 1999-01-19
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Last Modified: 2013-12-23
DHCP Clients are sending the DHCP Discover but our DHCP server is not responding.  Verified this by running Network monitor to capture packets.  This is occuring on not one but two DHCP servers both of which are having identical problems.  We have completely reloaded NT Server on one of the machines and experiencing the same problem.  Verified that DHCP relay agent is not running.  We feel we have covered all possible troubleshooting techniques to include re-installing DHCP.  All to no avail.  Any suggestions or links to a source of help would be greatly appreciated.
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Question by:saeeda
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by:hnminh
ID: 1571972
Did you check your hardware yet? Try with fix IP to if you can ping the server.
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by:saeeda
ID: 1571973
Tried that already, in fact the DHCP server is our DNS server too. Hundreds of clients are always connected to it.  The other server is a back server and it too has a fixed IP and internet access.
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by:netmage
ID: 1571974
I'll just verify a few important things with you and then move on to other details.

The dhcp servers must have static ip's.
Your scope's are valid ranges.
The scope has been activated.
Both dhcp servers are aware of each other.

If you have microsoft only clients, Wins is a better alternative to DNS and forces a netbios tcp/ip connection by resolving the wins database with dhcp.

Netmage
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by:tcalesa
ID: 1571975
A few questions. These may be basic so I apologize if I duplicate your previous efforts.

Do you have the latest SP?
Do you have available addresses?
Is the server multihomed?
Is relay running on the router?
Did DHCP ever work?
Are your routers 1542 compliant? (if routing is used?)
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by:tcalesa
ID: 1571976
Does the eve3nt viewer on the server give you any error messages?
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by:saeeda
ID: 1571977
We have totally isolated the DHCP server and the client to a single hub and still can't see any DHCP acknowledgments from the server.  We ran Network monitor to see if we got any DHCP requests from the client and we did, but no response.  The DHCP server has SP3 running.  All the scope addresses are valid and have been tried on other clients. DHCP has never been successful.  Server is not multihomed. Netmage: What do you mean by your last sentence? I'm not sure I quite understand it.  Could you be a little more specific. We have DNS running on the same machine we are trying to install DHCP on and that's what I meant when I said there were clients connected to it.  We do have another 3 WINS servers running on seperate machines.
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by:tcalesa
ID: 1571978
Did you install DHCP prior to updating with SP3? if not, re run the SP for kicks.

What parameters do you have set up in the scope?

Do you have any errors in the event log?
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by:saeeda
ID: 1571979
We haven't reinstalled SP3 after installing DHCP but will try it out. Will let you know how that goes.  The scope has global values of WINS, DSN, and Domain Name and a scope value of the router ID (gateway). We opened a new subnet on our network just for DHCP clients and it works too. We tried to put those IPs statically on the clients and they work just fine.  This is getting to be our worst nightmare.
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by:netmage
ID: 1571980
Regarding your question to me about the wins/dhcp config.

I just need to verify if the PDC is a wins server.

If so, and you you are using netbeui as a default protocol,The master browser list will be found here and  its Wins Service will not be enabled to see the other dhcp servers and therefore unless you make all wins servers aware of the dhcp servers everything will be resolved via netbios and bypass tcp/ip.Dns will be quite happy to work this way although slow but other (non windows)operating systems will fail to resolve names.

I can post a rather large article on how these 3 services need to be tied together if you wish. If i had the url i'd post that instead. But it will be at your request.

Regarding your isolation experiment.
Was tcp/ip the only protocol?


Netmage
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by:saeeda
ID: 1571981
Netmage: If you could please post that article you are talking about I will be grateful.  We are using TCP/IP and Netbeui as our protocols.  Our PDC does have WINS installed on it too.  
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by:saeeda
ID: 1571982
Netmage:  How do you make the WINS server aware of the DHCP server?
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by:saeeda
ID: 1571983
Netmage.  Okay we are making some headway now.  We got DHCP to work finally on our test LAN.  All that is connected together is just the DHCP server and one client via a small 16 port dumb hub.  When running network monitor on the DHCP server we get the DHCP discover but the server does not send any response.  This morning we changed our scope to the same subnet as our DHCP and it worked like a champ.  Any thoughts on that?
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by:saeeda
ID: 1571984
Netmage.  Okay we are making some headway now.  We got DHCP to work finally on our test LAN.  All that is connected together is just the DHCP server and one client via a small 16 port dumb hub.  When running network monitor on the DHCP server we get the DHCP discover but the server does not send any response.  This morning we changed our scope to the same subnet as our DHCP and it worked like a champ.  Any thoughts on that?
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by:Tim Holman
ID: 1571985
Just read the thread...
DHCP Discovers are broadcasted, so if they hit any routers / inteliigent hubs that do not have BOOTP relay enabled, they won't go through.
Sounds like you've a DHCP client on a different network to the DHCP server, and as there's no relay agent, they're not getting through.
It could also be that your scope is already used up !
Of course they HAVE to be on the same subnet, otherwise it won't work - BOOTP requests will just fly around on the subnet, never cross it onto another (as you've disabled BOOTP relay) and leave you in this situation.....



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by:sugdenj
ID: 1571986
Just thought I would say I saw similar behavior.  DHCP would assign IP addresses to JetDirect interfaces, but not to workstations.  Not a routing issue, since DHCP serve and workstation were on same subnet (same hub, even!).  IP addresses available for lease in the scope. NT 4.0, SP3 on both boxes.  Netmon confirmed broadcasts received by server, just no response.

I didn't solve it, as I departed that site 2 days later....it was very odd.
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by:tcalesa
ID: 1571987
saeeda,
OK You are trying to get DHCP to assign IP to a different logical subnet on the same physical network right?

IOW, You have a server with a NIC assigned address of 165.48.176.20 and SM of 255.255.255.0 but you have PC's running workstation on the same physical link that you wish to assign addresses from a different range like 165.48.177.XXX SM 255.255.255.0 Is that a correct assumption?

I may have seen a paper regarding this type of setup. I'll search for it while I wait for your reply.
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tcalesa earned 100 total points
ID: 1571988
Here's the paper. Please reject if it doesn't work.


From:
http://support.microsoft.com/support/kb/articles/q124/0/26.asp?FR=0
***************************************************************

The information in this article applies to:
Microsoft Windows NT Workstation version 3.5, 3.51, and 4.0
Microsoft Windows NT Server version 3.5, 3.51, and 4.0


SYMPTOMS
Windows NT Dynamic Host Configuration Protocol (DHCP) client IP address lease requests fails on a multihomed server configured with multiple logical IP networks on a single network interface card (NIC).

This logical multihomed system is a Windows NT Server with a single NIC configured with multiple IP addresses for one physical segment. If this server is also functioning as a DHCP server with active scopes configured for each logical IP network, DHCP client requests are filled until the scope defining the first logical IP address pool is exhausted. Further DHCP client requests fail to be filled from the pool of IP addresses available from the second or higher logical IP network scopes.



RESOLUTION
To resolve this problem, install a NIC in the DHCP server for each logical segment. Each NIC should be connected to the same physical segment and assigned only one logical IP address. As DHCP scopes are created they will be made available to the clients via the network interface card at this IP network. Also verify that IP routing has been enabled on this multihomed DHCP server.



STATUS
This is by design. This forces clients residing on a physical segment to acquire IP addresses that are within the same IP network scope.

More Information Microsoft Windows NT Server 4.0 Service Pack 2 includes the ability to create DHCP superscopes, which allows the administrator to group scopes together. This eliminates the need of multiple adapters to service multiple scopes.

For more information on superscopes, please see the following article in the Microsoft Knowledge Base:

Article : Q161571 Description: Using DHCP "Superscopes" to Serve Multiple Logical Subnets
 

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