If you have two interfaces, you must have two IP addresses.

Letīs assume youīre using ethernet only, with address 9.5.5.3 (A class);
If you want to access (ping ou telnet, or whatelse) a C class network (192.x.x.x) you must have two parameters: gateway and destination;

By gateway I mean a machine (a server or a router) that connects your AS400 to the other net; by destination, I mean the address or domain that you wanna reach.

Letīs suppose you have a gateway (connecting the two nets) with two ethernet cards, the first 9.5.5.1, the second, 192.168.0.1;
To acccess the C class network, you have to configure a route (CFGTCP, option 2), with dest: 192.168.0.0, mask 255.255.255.0, gateway 9.5.5.1;
With this, you can reach any address between 192.168.0.1 -> 192.168.0.254;

Good luck.