Ethernet Switches & Routers

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Occasional Contributor
Posts: 15
Registered: ‎06-27-2014

Help needed on DHCP Relay

Hello All,

 

I have configured ICX7450, with VLANs 1,5,6,7 and 9. The default-vlan has been changed to 4001.

 

Port 1/1/2 has configuration - Tagged 5,6,7 and Dual-mode 1.

 

Port 1/1/13 - untagged vlan 1

 

A Wireless controller has been attached to Port 1/1/2 and it is having Tagged VLANs 5,6,7 for Users, Management and Guests respectively. In wireless, we have configured multiple SSIDs, which are attached to different VLANs.

 

A DHCP server (IP = 10.100.1.11/24) has been attached on Port 1/1/13 to provide IP to all the ports. Also, a Virtual Interface for every VLAN has been created and each given IP address (10.100.X.1, where X=VLAN ID).

 

Finally, in all the virtual interfaces defined, the "ip helper address" mentioned is 10.100.1.11.

 

The problem is that I am getting IP only on VLAN 1 from DHCP Server, but not on VLANs 5,6,7. I don't know what part I am missing, but it would be great if someone could help.

 

Please Note: - The network has gone live and all the desktops and servers are connected on VLAN 1. If there is any possibility of downtime during the configuration, do remember to mention that.

 

Many thanks in advance,

 

Aashish.

 

 

Frequent Contributor
Posts: 104
Registered: ‎07-12-2011

Re: Help needed on DHCP Relay

[ Edited ]

What wireless controller?

 

Cisco's wireless controllers can define (override) DHCP settings, also they can do DHCP proxy which can cause your issues

 

Here is a link that explains it's function


http://www.cisco.com/c/en/us/td/docs/wireless/controller/7-4/configuration/guides/consolidated/b_cg74_CONSOLIDATED/b_cg74_CONSOLIDATED_chapter_0110.html

 

Occasional Contributor
Posts: 19
Registered: ‎05-23-2013

Re: Help needed on DHCP Relay

In addition to what John wrote, have you connected a laptop or workstation to the AP with the IP already configured for the scope it should be on and tested connectivity that way? IE., can you ping your gateway, or your DHCP server?

Contributor
Posts: 40
Registered: ‎01-28-2013

Re: Help needed on DHCP Relay

To tack on to what they said, you could do some troubleshooting to determine if your problem is the wireless controller, or your DHCP/VLAN setup.

 

You could take some unused ports on your Brocade and assign each one as untagged in each VLAN (like port 1/122 untagged in VLAN  5, port 1/1/23 untagged in VLAN 6, and port 1/1/24 untagged in VLAN 7. Then plugin a laptop to each of theose ports and see if you can get a DHCP address. It would also do good to watch the logs on the DHCP server to see if the DHCP request comes in, or a DHCP offer goes out.

 

Write us back and let us know where you ar eon this now.

Occasional Contributor
Posts: 19
Registered: ‎05-23-2013

Re: Help needed on DHCP Relay

Also, not trying to add too much to your troubleshooting plate, but one thing I meant to add in my earlier post but I got interrupted mid-thought, have you confirmed your DHCP server is set up to handle each scope? Again, not trying to overload you, but this is something that is easy to check and confirm that each scope has been configured and is ready to handle all helper traffic sent its way.

Occasional Contributor
Posts: 15
Registered: ‎06-27-2014

Re: Help needed on DHCP Relay

Thanks to all the guys for their feedback and response. Definitely made me learn in the process through your responses.

 

Since the support was being done on remote, the following was done to resolve the issue: -

 

Wireless Controller used is that of Ruckus (named: ZoneDirector).

 

Issue 1: Since the uplink was done temporarily on Copper Ports (instead of Fibre), the guy at the site had wrongly connected the ports from L2 to L3. It was connected on an untagged port (carrying VLAN 1). We verified this by specifying untagged VLAN 5,6,7, etc on a port on L2 Switch and connecting PC to it and then trying to obtain IP from DHCP Server. The uplink was passing only VLAN 1.

 

Issue 2: Ruckus controller talks to their Access Points on VLAN 1, by default. Therefore, which ever ports on the switch had APs connected, Dual-mode 1 on them were defined, and also on the Port of L3 Switch connecting the Wireless Controller.

 

Doing the above two resolved the problem.

Occasional Contributor
Posts: 15
Registered: ‎06-27-2014

Re: Help needed on DHCP Relay

[ Edited ]

Yes, John20. The suggestion helped.

 

Yes GB_KIR, we ensured that DHCP could handle each scope.

 

Initially, when we had connected a laptop directly to L3 on different ports catering to different VLANs, IP was getting received from DHCP Server.

 

Only when we tried to specify various untagged VLANs on L2 Switch, then IP was not being received, and that made me look into the cabling issue, about which I have replied.

 

Life can be funny sometimes... You look everywhere for a solution, except under your nose Smiley Very Happy

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