Getting wrong IP when move from VLAN to another

[katab]

I'm facing strange problem in our NEW network , when users moves from VLAN 16 to VLAN 17 they still getting IPs from DHCP scope of VLAN 16 . Same for other VLANs.

DHCP server---- win 2003

Switch ---------cat3560

Core cat6509

When I give the user static IP from VLAN 17 ( new VLAN ) it works fine , but when I tray to go back to dynamic does not work.

I use commands at users workstations win 2000 or XP

ipconfig/release

ipconfig/renew

ipconfig/flushdns

and also i tray to assign static gateway ( VLAN 17 gateway) and getting IP Address from DHCP but still it i will get ip from VLAN 16.

when I check event log logs i found error Source : DHCP Event ID :System 1003 . but i can ping DHCP server and I am getting an IP in old VLAN ( 16 ).

I face same scenarios for other VLANs.

[amit-singh]

Hi,

Do you a scope defined for Vlan 17 in your DHCP server.

Where is DHCP server placved i.e in which Vlan and connected to which switch.

Please paste teh config for the switch to better understand the issue and if possible also a N/W diagram.

regards,

-amit singh

[andrew.butterworth]

Have you implemented SuperScopes on the DHCP Server? If you have this is likely to be the problem - remove them and make each scope unique. Superscopes are useful where you have Secondary IP addresses on interfaces but cause the problem you are experiencing if you don't.

Andy

[katab]

Thanks all

To be clear I get an IPs from DHCP server .

I face the problem only one chang Vlan .

Andrew

I'm using SuperScopes , do you have any document about this issue . I will try to make unique scope for each VLANs.

Thanks & regards

[p-coelho]

Did you check information in windows 2003 about the DHCP scopes ? you must define the DHCP scope with vlan 17 gateway and other DHCP scope with vlan 16. The Ip helper address in both vlans must be the ip address of DHCP Server.

[Richard Burts]

From your description of the problem I would think the issue is more likely on the DHCP server than it is to be on your switch or router. Is the DHCP server set up with multiple scopes? And does it differentiate the relationship between the scopes for the various subnets?

HTH

Rick

[katab]

Now we are sure that it's from DHCP , I still using super scope , we solve the problem following this steps:

1- before PCs moved to another VLAN ipconfig/release must be used and shutdown PC.

2- Remove the record from DCHP server

3- Connect the PC to other VLAN and will get correct IP.

We are planning to use different scope for each VLAN , I will let you know if it is work fine.

Regards,

[paddyxdoyle]

Hi,

I have experienced problems similar to this.

Some PC's would get the correct IP address when changing VLANs yet others wouldn't.

We never implemented a fix for this and indeed we followed the steps you mentioned about however i think there was a fix for this from Microsoft which from memory was called "agressive NAKing" but at the moment i can't find any information on this.

There is a doc on the MSoft site which discusses why this DHCP issue happens but it only talks about using "ipconfig release/renew" to fix the issue.

http://support.microsoft.com/default.aspx?scid=kb;en-us;167014

I'll have another dig around and see if i can find any further info.

Rgds

PJD

[andrew.butterworth]

If you remove the SuperScope configuration you will also remove this problem. I did a lot of testing with this on the last project I worked on and this was a problem with SuperScopes. They are designed for use when you have secondary IP addresses configured on interfaces. Create individual scopes and the problem will be gone.

Andy

[katab]

Thanks all

Andrew yes it is related to the superscope .

Best Regards,