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 From:  "Chris Buechler" <cbuechler at gmail dot com>
 Cc:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Problem with configuring Static IP WAN
 Date:  Sun, 25 Jun 2006 15:54:54 -0400
On 6/25/06, Neil Gardner <Neil at neilnz dot com> wrote:
> My provider requires me to specify a /32 Mask for the WAN port... I don't
> appear to be able to do this in 1.22... (I can only specify /1 through /31)
> Am I missing something silly or is this a limitation at the moment?
> I wouldn't have thought /32 support was that rare...

You resolved the issue, but for the sake of the archives...

 A /32 is a single IP.  A /32 cannot talk to anything else, as there
isn't anything on its local network including no gateway.  Your
default gateway has to be within the subnet of your WAN IP.  There are
some exceptions to this that I won't get into (dial up connections
commonly use /32's).

Suffice it to say, on most Internet connections, you don't really have
a /32 WAN IP, especially with static IP's.  Some OS's and firewalls
just happen to work this way with static IP's, but only because they
ignore the subnet mask and they'll use any old default gateway you
throw in there.  The smallest actual subnet mask you can have under
most circumstances is a /30, one public IP for you, one for your ISP's
router.  /31's can do the same under some circumstances, but eliminate
the network and broadcast IP's and aren't widely used.