Network (192.168.1.0/24 eth1) is the server that has access to the resources of the provider (for example 220.127.116.11/23 and all of them are using eth0) and access Internet through pptp.
Connect via pptp, there is an interface called ppp0.
For routing of Internet writing:
route-net 0.0.0.0/0 dev ppp0
The Internet works, internal resources penguasa.
Prescribe to it rules for masquerading all computers on the internal network could access the Internet through this server as a gateway.
iptables-t nat -A POSTROUTING -o ppp0 -j MASQUERADE
From the Internet, but there is no access to the resources of the provider (judging by traceroute packets on the gateway 192.168.1.1 not go away). What rule can do this?