ADSL + Client connect with Internet problem

[edwardspl at ita.org.mo]

Dear ALL,

There is a Linux Gateway Server ( FC9 ) :
eth0 connect with ADSL modem ( Dynamic IP )
eth1 connect with HUB

[root at xxx ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
BROADCAST=192.168.0.255
IPADDR=192.168.0.254
NETMASK=255.255.255.0
NETWORK=192.168.0.0
ONBOOT=yes
NM_CONTROLLED=

[root at xxx ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=static
BROADCAST=192.168.1.255
IPADDR=192.168.1.254
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
NM_CONTROLLED=

For NAT setting :
iptables -A POSTROUTING -t nat -s 192.168.1.0/24 -o ppp0 -j MASQUERADE

BUT All of clients can't ping ISP's IP or domain :
C:\>ping 202.175.xxx.xxx

Pinging 202.175.xxx.xxx with 32 bytes of data:

Reply from 192.168.1.254: Destination net unreachable.
Reply from 192.168.1.254: Destination net unreachable.
Reply from 192.168.1.254: Destination net unreachable.
Reply from 192.168.1.254: Destination net unreachable.

So, would you mind to help ?

Thanks !

Edward.