I have two external connections, one is internet (eth1 velox-ip: 192.168.0.10) and the other is a company intranet (eth0 ip: 10.1.240.x) and a local (eth0 in the range 10.1.240.x) I want to put it to work as follows:

one computer with 2 network cards input for velox and intranet, and other output for the company pcs. to work all in one conection.

i used the command route add default gw 192.168.0.10 to leave the internet as the main gw, and put it in rc.local:

echo 1> / proc/sys/net/ipv4/ip_forward
iptables-t nat-A POSTROUTING-o eth1-j MASQUERADE

if internet works,the intranet network doesn't works, and if i put the intranet gw as default, the internet conection doesn't works. how can i put the two conections to works together.

This sounds like two connections. Are there two or three NICs?

You are routing packets to your own eth1 port. That doesn't sound right.
You are missing spaces in the line you posted. That command would not work.

There are 3 conections, 2 external(but one has internet and other is an intranet) and 1 local. So i wanna share the two external conections over the lan conection.