Alias in different subnet on card

[Wayne Pascoe]

Hi all,

I'm running a firewall at the moment using FreeBSD 5.2.1 and IPFW. I
have 3 interfaces in the machine. 

I need to be able to firewall a 4th range of IP's. I have tried to do
this by adding an alias to xl1, but this hasn't worked. If I add the
alias with a mask of 255.255.255.255, no other machine can ping the
alias. I also see the following in /var/log/messages
Mar  8 18:02:13 styx-tmp kernel: arplookup 19x.xxx.xxx.196 failed: host
is not on local network

The primary IP on xl 1 is currently 19x.xxx.xxx.1 and the mask on there is
255.255.255.128 (/25)

If I add the alias with a mask of 255.255.255.240 (/28) which is the
correct mask for this subnet, and the mask that all other machines use,
then I am able to ping this address. However, at this point, no
forwarding appears to take place for machines using this IP address as
their default route.

Is there any way to use an alias to do firewalling like this or do I
have to get another network card? The problem with another network card
is that will mean a whole new machine as I'm out of slots in this one.

Thanks in advance ?

-- 
Wayne Pascoe
Microsoft complaining about the source 
license used by Linux is like the event 
horizon calling the kettle black - adamba on k5