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DHCP problem with VLANs

Posted on 2013-06-24
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Last Modified: 2013-07-07
I have a win2k8r2 DHCP server and I'm running into a particular issue with our user VLANs. We have made a new VLAN for user machines. users are successfully receiving IP addresses from the DHCP server on this VLAN. The switches are Cisco Nexus 5548s using layer 3. We have commands on the VLAN below.

interface Vlan101
  description User Computers
  no shutdown
  no ip redirects
  ip address 10.120.1.2/24
  ip passive-interface eigrp ...
  hsrp version 2
  hsrp 101
    authentication md5 key-chain ....
    preempt
    priority 105
    ip 10.120.1.1
 ip dhcp relay address 10.1.1.61  <-- win2k8r2 DHCP server

My problem occurs when the user disconnects their laptops from their desk ports which are mapped to this VLAN and attempt to move to another room with a different VLAN such as a conference room. The conference rooms are on a different VLAN but utilize the same network infrastructure and same DHCP server.

What appears to be happening (I think..) the user has been provided an ip address such as 10.120.1.10 on VLAN 101, when the user connects to the conference room port, the request for an IP from the laptop is sent to the same DHCP server, it recongnizes the host and knows it already gave it an IP address so it tries to give the host the same IP as before (10.120.1.10) but, that IP is invalid for the subnet so there's a problem.

I'm certain there's a way to fix this but I wasn't the one who setup the DHCP server so I'm unclear of how to resolve. any help is appreciated!
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Question by:jbla9028
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2 Comments
 
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pony10us earned 2000 total points
ID: 39271768
The issue is the DHCP server.

Two things jump to mind:

1. Do you have it set to release on shutdown? (see http://technet.microsoft.com/en-us/library/cc977398.aspx)

2. Are both VLAN's in the same scope?  (There was a discussion on the Cisco board a couple of years ago about this exact issue:  https://supportforums.cisco.com/thread/147847)
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by:jbla9028
ID: 39305979
That was the exact issue. Thanks! I removed the scope from the super scope and it worked!
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