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DHCP on a Cisco Catalyst 3750

Posted on 2010-09-20
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Last Modified: 2012-06-27
I'm trying to get the DHCP server to work on Cisco IOS. The IOS is 12.2(25)SEE2)  running on a Catalyst 3750 switch.   (We usually us Microsoft DHCP.)

I have a test Vlan (VLAN99) defined.   When I assign a static address (10.67.99.1) to my workstation, I'm able to get everywhere I need to, so the VLAN seems to be set up correctly.    But when I set my nic to use DHCP, I get the default 169.x.x.x address.  It's behaving like the port is on the wrong vlan, but it's the same port that works fine with a static address.

Here's how I have DHCP configured on the Cisco IOS.

ip dhcp pool RESTRICT
   network 10.67.99.0 255.255.255.0
   domain-name restrict.com
   dns-server 10.67.0.7
   default-router 10.67.99.247
   lease 7

The client is Windows XP   SP3.

I'm beginning to wonder if there's something in our Active Directory GPO that only allows us to accept IP addresses from DHCP servers already registered in AD??


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Question by:asd-dave
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Darius Ghassem earned 42 total points
ID: 33717642
Remove the workstation from the domain then see if you get an IP address that will determine if Windows Network is causing the issues but I doubt it is the Windows Network.
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Assisted Solution

by:bjove
bjove earned 83 total points
ID: 33718052
use
#debug ip dhcp server events
from console, to check for problems with Cisco DHCP server
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Assisted Solution

by:Rant32
Rant32 earned 83 total points
ID: 33718109
That default router you specified (10.67.99.247), is that the 3750's VLAN interface?

If it's not, I believe that the VLAN interface needs an IP address in the network you use for DHCP so it can bind the DHCP pool to the specific VLAN.

There are no settings I know of to restrict the client to the type of DHCP server you want to use.
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Assisted Solution

by:jjmartineziii
jjmartineziii earned 42 total points
ID: 33722256
Your router must have an IP address on the 10.67.99.0 255.255.255.0 network.

If you don't, you need to use "ip helper-address <ipofyourrouterwithdhcp>" on your gateway's interface for the 10.67.99.0/24 network.

This will work. I use dhcp in this type of environment daily.
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Author Comment

by:asd-dave
ID: 33800140
Thanks all... I was out of the office for a week.

1.  Removing workstation from the domain had no effect.

2.  I entered the debug statement, tried getting an IP address, and got no output.

3.   10.67.99.247 is an IP address of a virtual interface on our core switch.    If I give the workstation a static ip address (say... 10.67.99.5), everything routes as expected.    But just to rule it out, I created another virtual address on the "local" 3750 of 10.67.99.246, and changed the default-router parameter to that address.  (The local 3750 is where dhcp is configured).   This also resulted in no change, and there was no output on the debug screen.

4.  I don't believe we need a helper address because we're dealing with a layer 3 switch, routing is enabled, and the DHCP scope is defined on that same switch.   (So VLAN99 exists on the switch, the scope 10.67.99.0/24 is defined on the same switch, and the port the workstation is plugged into is on VLAN99.   (switchport access vlan 99)

5.  Just to rule out any strange quirks on my workstation, I am now trying it on a different workstation, and getting the same results.

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by:bjove
bjove earned 83 total points
ID: 33800417
It seems like the VLAN 99 is not created.
Enter in config mode:
Rounter(config)# Vlan 99
#exit
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by:Rant32
Rant32 earned 83 total points
ID: 33801197
ip dhcp-server wouldn't be configured, so it seems, that would explain why there's no debug output.

The right debug statement should be, from: (pdf alert) Catalyst 3750-X and 3560-X Switch Debug Commands

[no] debug platform ip dhcp all|error|event|packet|rpc

You could start with error logging first, then add event and packet until eventually something wrong turns up. It should at least reveal what's going on in the switch.
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Author Comment

by:asd-dave
ID: 33802604
It seems like the VLAN 99 is not created.
Enter in config mode:
Rounter(config)# Vlan 99
#exit

It wouldn't let me because this switch is in vtp client-mode.    I went ahead and issued the command on the switch that's in server-mode.    No difference.

[no] debug platform ip dhcp all|error|event|packet|rpc

I issued the command with "all" to get all information.    Next I put the selected port in vlan 99 and tried to get an IP address.   Ddin't get an IP address, and got no messages from the console.

As an aside, I checked the native vlan.  (Shouldn't matter in this case, but thought I'd check.)     While I know it's not a good practice, the native vlan is 1 on all switches.

Guess I'm not missing something obvious??  
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Author Comment

by:asd-dave
ID: 33809882
Thanks everyone for your help.   I knew it had to be something simple.   I logged a case with Cisco, and the tech saw that I didn't have the DHCP service turned on.   (If I didn't see a line in the config that said "no service dhcp", I didn't know to turn it on.)    In global config mode, I entered "service dhcp" and everything magically worked!
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Author Closing Comment

by:asd-dave
ID: 33809902
Cisco TAC solved question.  But thanks everyone for your help.
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