ip address and router address

The firmware on the Express is behaving correctly.. it cannot put in numbers that are inconsistent.

Unfortunately due to ISP breaking fundamental network rules.. the routers have problems.. Linux and NetBSD have issues when you break the rules.. The later is used in the Express..

Usually it will handle it ok by dhcp.. but if you are forced to do it manually.. sorry it isn't going to work.

The submask is used exactly to indicate what is the subnetwork and what is the global domain. In other mac environment, like macbook pro, mac mini, mac pro, macbook air, the configuration is perfectly ok and giving no problem at all.

I have run into this problem in Linux based routers.. since forever. I think the subnet mask is not being read or read correctly.. and it will take the IP and assume the gateway must be in whatever is the standard class for the IP.. and that usually means /24

When I have been able to work around it.. it is by providing a static route.

As you know.. apple routers hide all controls.. everything.. you cannot access the route table to fix it..

(Actually you can but how are your soldering skills??)

If you could get into the route table you could fix it.

Let me say my subnetting is not something I have done for a long time.

I tried your values in a airport.. and they didn't work.

I fixed it by opening the subnet ..

This is a consistent result. And it works.