IPCHAINS

[Luis Gustavo Madrigal Salazar <tavo@scratchy.emate.ucr.ac.cr>]

I'm trying to install a NAT server in my box and I'm using ipchains 1.3.9
I want the private netwrok 192.168.1.0/24 to be able to get to the
internet using my linux box as a gateway. The L:inux only has one network
interface (so I set up an alias using: ifconfig eth0:0 192.168.1.1)
my input chain is using ACCEPT as the default policy and no rules.
the output chain's policy is ACCEPT, no rules.
the forward chains's policy is DENY and it has one rule:
MASQ all protocols source 192.68.1.0/24 destination 0.0.0.0/0 ports n/a

the Linux box responds when I ping it from a client (ping 192.168.1.1)
and also the Linux can reach all the clients.
But the clients can get out to the internet!.
What I'm I doing wrong????????