DHCP problem with VLANs
Posted on 2013-06-24
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.
description User Computers
no ip redirects
ip address 10.120.1.2/24
ip passive-interface eigrp ...
hsrp version 2
authentication md5 key-chain ....
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!