WAN: Single IP address for WAN with /32 netmask not possible?

[zette]

I have adsl line attached to my zentyal WAN interface that is configured with bridge mode. I have static IP address provided by my ISP, but normally it is provided by modem with dhcp.
Since it is not very reliable, I tried to manually configure the WAN interface, with that IP address, but 32(255.255.255.255) netmak value is not possible to configure through gui.
Is there any other way to cofigure the interface the way I want, and be sure that my configuration won't be overriden next time I change some things with zentyal gui?

Right now I do it manually with ip addr, and route, but it is not permament solution.

[ichat]

are you sure your provider tells you to use a subnet mask of  255.255.255.255 - as to my best knowleged that would leave NO hostspace,  and no broadcast adres and thus no network...

the least any network requires is  a netID, a broadcast ip, and for it to function right 2 host adresses, (1 would be a strange and useless network so lets update that to 2 host adresses, right?)

making the highest usable subnet not 255 but 252..   /30 (could this be why it wont work for you...

[christian]

Ichat is correct here: netmask is not showing IP range that is allocate to you by your provider but range in which your IP works, and this is totally different. Guessing netmask might not be obvious and I would suggest that you have a look at your IP stack once you get an IP. netmask will be shown here 

However... do this only if you are 100% sure that your IP is a static one 

[zette]

I know how the subnet works, and what it does need. Unfortunately this ip address I have is only provided at isp dhcp (adsl modem) level, which sets it with /32 mask, and designated gateway in routing table entry.
For me it looks that gw is from another address pool, unless the isp is using /16 network for its dhcp leases.

I'd rather not put /16 netmask in my configuration, and if You can not see any other way, I'll write some script to set interface address and routing on start, and leave the interface without configuration in zentyal, though loosing all gui-friendly firewall/proxy/etc.. features on