Disable Key Exchange for Subnets R65

[Halty]

I've perform a migration upgrade from R55 AI to R65, Smart Center fine and all bar one Gateways fine. One Gateway I will not be able to upgrade for a while as it is a long way remote (and a few other issues). Communication to the Smart Centre Good and our corporate site-site works fine. However from this gateways we have a VPN to a cisco Box which is fails when negotiaiting.

After running some tunnel tests I can see that we are sending as a subnet x.x.x.x/255.255.255.248 while the Cisco is expecting x.x.x.x/255.255.255.255.

Now normally i would have Disable Key Exchange for Subnets but when I check the Interoperable device the option no longer appears. How do I disable now ?

Thanks In advance