wlsm redundancy

[dmaillard]

Hi,

I want to implement the redundancy between 2 wlsm in 2 Cat6509. I created a trunk link between them. A external dhcp server is in the network to give the IP infos on the mobile clients. Inside those IP infos I only can setup a default Gateway that should be the IP address of the tunnel interface in the Sup720 module.

With the redundancy concept I need to configure 2 tunnel interfaces with a different IP address (1 per Sup720 module). How can I configure a same IP address in both tunnel interfaces ? HSRP is not configurable and the config of the same IP address is also not possible due to the duplicate IP address. What are the possible solutions ? Any ideas ?

Thanks for helps,

Domi

[vblavet]

Hi,

There is 2 solutions to solve the problem.

- First deliver several IP default gateway from the DHCP server to the mobile clients. If the first C6k is down, the client will use the second default gateway. The problem of this solution is that the client will have to understand the 2 default values and be able to use it.

- The second is to use the same IP@ for the tunnels on both Sup720. This seems strange but you never have both tunnel up at the same time, so you don't really have a duplicate IP. You have a duplicate IP in the configuration but only one is up at a time.

Hope this helps,

Vincent

[dmaillard]

Hi Vincent,

I agree with you but as soon I configure the same IP address in both tunnel interfaces I receive a log message about a duplicate IP address. That is due to the routing table where both IP address are directly connected through the tunnel interfaces.

Thanks for your help,

Dominique

[simonstoll]

Hi Dominique

I used a third approach. The WLSM answers for any IP adresse expect the one from the client with his own mac-adress (kind of proxy-arp). So you can asign the client one default-gateway but you can use two differt IP's as the gateway under the Mobility Tunnel Interface. Sounds strange, but it works! I also don't understand why Cisco isn't offering a better approch (HSRP) for this problem, but I'm using the redundant WLSM Blades this way since this plattform is available.

Simon

[luc.vanacker]

Hello,

We have the same concerns, we use pda which does not support two default gateways, what do you mean when you write : "you can asign the client one default-gateway but you can use two differt IP's as the gateway under the Mobility Tunnel Interface".

assign a virtual ip address which is not linked to tunnels ?

thanks for your comments

ps: could you reply with an extract of the config ?

thanks

Luc

[jroyster]

I just use the same IP address on the tunnel interfaces. Works like a champ.

If you have redundancy configured properly (you can check with "show mobility stat" on sup720) you will not get any duplicate IP errors.

The tunnel interface on the primary 6500 should be in an up/up state. The secondary will be in a UP/DOWN state and is not pingable.

If you are getting duplicate IP errors my guess is the WLAN VLAN is not trunking properly (possibly not allowed/pruned on the trunk) and the WLSMs are unable to send hellos.