2 variables in R. Ziegler's book

[Michael Boyd <Michael.Boyd@maunsell.co.uk>]

Hello,

I am constructing my ipchains ruleset at the moment following the
example in R. Ziegler's Linux Firewalls.  In the section on smurf
attacks he uses 2 variables which seem not to be declared anywhere,
$NETMASK and $NETWORK.

I have tried entering...

echo $NETMASK
and
echo $NETWORK

at the command line to see if these are variables declared elsewhere but
get nothing.

Ziegler's examples are based on Red Hat so I thought they *might* exist
in Red Hat but not Debian, but that is a shot in the dark.

Can anyone tell me what they are?  I presume NETMASK is fairly obvious
but don't know what to enter for NETWORK.

Thanks

Mike

PS I have looked in the errata at www.linux-firewall-tools.com and can't
see any mention of it there.