Layer 3 and WISM failure

plearmouth · ‎03-20-2007

Hi

I'm designing a relatively large wireless deployment and it has been sized for approx 4K users.

The network is to be layer3 with the intent of using AP groups to reduce the size of the broadcast domain.

Are these assumptions then correct:

1. During the failure of a WISM, all AP's reboot and reconnect to the secondary WISM. Clients reassociate and request new IP addresses from the new subnet.

2. If 1. is correct then it is safe to presume that with a third controller I would need 4K * 3 = 12K addresses (worse case).

3. As I am unlikely to be allocated 12K addresses the workaround would be to place all the WISM's AP interfaces into the same VLAN (layer2) so DHCP scope remains the same, and keep layer3 between WISM and AP's.

Thanks in advance.

Paul

wong34539 · ‎03-26-2007

Actually your assumptions are correct. But still there is a restriction on the number of APs that could join with a WISM. So, based on that I think the no of APs failing over to a secondary WISM will very.

prakashj · ‎04-11-2007

Hi paul,

1. During the failure of a WISM, all AP's reboot and reconnect to the secondary WISM. Clients reassociate and request new IP addresses from the new subnet.

A)The Cisco WiSM consists of two Cisco 4404 controllers; therefore, the IT staff must be aware that two separate controllers exist on a single module. The first controller is considered the WiSM-A card, while the second controller is considered the WiSM-B card. Interfaces and IP addressing have to be considered on both cards independently. WiSM-A manages 150 access points, while WiSM-B manages a separate lot of 150 access points. These controllers can be grouped together in a mobility group, forming a cluster,So the WISM will provide the L3&L2 fast roaming,And ther will not be any downtime for clients.Client will automaticaly get registed in another controller immmedatly.

Pls refer the belwo mentioned URL,it may help you.

http://www.cisco.com/en/US/products/hw/modules/ps2706/prod_technical_reference09186a0080702fe2.html

I hope this will you..

Thankx&Regds

saji k.s

DOHA