eth0 & eth1 won't work at the same time

Warrick scribeth:
 > Kernel IP routing table Destination Gateway Genmask Flags MSS Window 
irtt Iface
 > 135.7.0.0 * 255.255.0.0 U 0 0 0 eth0
 > 135.7.0.0 * 255.255.0.0 U 0 0 0 eth1
 > 127.0.0.0 * 255.0.0.0 U 0 0 0
 > lo default * 0.0.0.0 U 0 0 0 eth0

OK. First a word about the choice of IP addresses.
For private networks, you should be using the following ranges :
Class A 10.0.0.0 to 10.255.255.255
Class B 172.16.0.0 to 172.31.255.255
Class C 192.168.0.0 to 192.168.255.255

There are good reasons for this; one of which is that these addresses
will not be known on the internet. Also, AFAIK, there are some routers
where NAT only works on the private IP address range.

Back to the problem. As you see from the routing table the entries for both
interfaces are the same. The routing table is evaluated top to bottom; so
everything for 135.7.x.x is going to eth0.
One solution would be this :
route add -net 135.7.16.0 netmask 255.255.255.0 gw 135.7.16.121

Margit