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New Member

DHCP Renew Problem


I have a network with several Catalyst with a odd problem, I have several VLAN's and when I remove one PC from VLAN x to VLAN y the PC should get an IP address from the DHCP pool ( the DHCP Server is W3K) that corresponds to the VLAN y, but even after a reboot to the PC it still gains an IP from VLAN x. As anyone come across this problem before ?

Best Regards

Hall of Fame Super Silver

Re: DHCP Renew Problem


What you describe is quite unusual. So I have a few questions just to clear up some aspects of the situation.

1) Can you verify that the PC is configured for DHCP and does not have a hard coded address?

2) Do other PCs in VLAN y successfully get addresses from the DHCP server?

3) Can you do these commands and capture and post the output while the PC is connected on VLAN y:

ipconfig /all

ipconfig /release


ipconfig /renew




New Member

Re: DHCP Renew Problem

Hello Fausto...

I had the same problem months ago...

Do not worry, the problem is in your DHCP Server, not in your Routers or Switches, What you have to do is to review your scopes in the DHCP Server. In Computer management Check the DHCP server configuration. I guess you will see here your scopes inside your superscope 0, what i had to do was to delete superscope 0.

I hope this help you. Jesus Ponce

New Member

Re: DHCP Renew Problem

I'll ask my customer to do that i.e. move the DHCP scopes outside the superscope.

By the way I can't capture the ipconfig /renew or the ipconfig /release output because I don't have physical access to the site, but based on a detailed with dump debug I made on the Catalysts the funny thing is the request goes out to the DHCP server, the DHCP server offers a IP address from VLAN y and voil? the PC gains an IP from VLAN x funny isn't it ? I tried to disable any DHCP related functions like service DHCP, no no ip dhcp snooping verify mac-address etc. To no avail.

So I'm going to wait for the customer to move the scopes and then I'll provide you both with feedback.

Thankx for the help.

Best Regards

Fausto Oliveira

New Member

Re: DHCP Renew Problem

That is, I understand. For example you have a host with an ip x.x.2.1/24, then you move this host to other segment (x.x.3.0) and you still have the ip x.x.2.1. And the release/renew commnad does not have effect. I used to erease at first the ip x.x.2.1 from the dhsp server and then connect the host to the new segment to obtain the new address.

see u later