DHCP Required

bsturges1 · ‎03-02-2009

This question is regarding DHCP required and mobile supplicants in an LWAPP architecture environment. Assume DHCP required is set to true. Assume the supplicant is powered on and receives its IP address. The client then roams to a new BSS (BSS2) in the same subnet and does a DHCP request and receives notification it can continue using the one it has leased (assume it has not expired).

Question: If the client has a BSS table and roams back to the first BSS (BSS1). The client determines that it currently has an IP from BSS2 that is in the same subnet as the previous IP it was provided from BSS1 and so chooses to use the existing IP... and not do a DHCP request.

How do the controllers and APs handle this client that they have seen on this AP before and provided it an address before?

migilles · ‎03-02-2009

This is not how DHCP required works.

Don't have to re-IP for every roam.

But when the session starts or ends, the client must re-DHCP as the WLC is serving as the proxy. Packets will not be forwarded to/from the client until then. This is not recommended for voice deployments, but you can enable this for your data SSIDs. If enabled for voice, then the potential for no way voice could occur if the session is ended via deauth or timeout.

bsturges1 · ‎03-02-2009

Do you have any documents on this feature? Appreciate the quick reply.

migilles · ‎03-02-2009

The 5.2 WLC Config Guide is @ http://www.cisco.com/en/US/docs/wireless/controller/5.2/configuration/guide/Controller52CG.html.

Is also documented in the 7925G Deployment Guide not to enable for the voice SSID @ http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7925g/7_0/english/deployment/guide/7925dply.pdf.

bsturges1 · ‎03-02-2009

This is great stuff. How about documentation on something that Assurewave has completed testing on. The latest being 4.2.176 to date?