It is right, if you router is behind another router, you also need to configure the other router.
Are you sure the router you are configuring is directly connected to the world wide web?
Doing a trace route could help identify it, here is mine to some ip:
Code:
Tracing route to 49.34.5.178 over a maximum of 30 hops
1 <1 ms 1 ms 1 ms name.home [192.168.0.1] <-- 1. this is my home router my computer is connected on
2 9 ms 6 ms 7 ms name.net.br [127.115.211.250] <- 2. this is my world wide web address my router is connected on
3 8 ms 8 ms 17 ms name.net.br [127.115.223.191]
4 48 ms 42 ms 24 ms name.net.br [221.22.64.97]
5 23 ms 25 ms 20 ms 246.52.252.232
6 160 ms 167 ms 136 ms 3.153.3.143
7 * * * Request timed out.
8 * 319 ms 288 ms ae-1-51.ear3.London2.Level3.net [4.69.143.198]
9 264 ms 265 ms 257 ms www.keek.com [195.50.117.34]
10 351 ms 358 ms 402 ms 103.198.140.26
11 387 ms 373 ms 358 ms 103.198.140.165
12 * * * Request timed out.
13 * * * Request timed out.
14 * * * Request timed out.
If the number 2. is your ISP's router, instead of the world wide web, you need to setup it (if it allow you) to perform the port forwarding also.