Ip cam not reachable with my routers

[umby75]

Hi, I"m not an expert on networking and I'm looking for a patiently help...
I'm using two routers:
RouterA is Huawei mod.DN8245f2 (Fastgate) is connected to Internet and an ethernet output is connected to
RouterB (the Fritzbox 7530) into Lan1/Wan ethernet port to share internet connection.
I'm looking for connect my ipcam connected to an eth port in RouterB.
I've tried to set either the RouterB as router or Ip client and for both modes I can reach the camera only into my Lan but over internet I'm not able to connect yet..
Recently I've changed my ISP and my new one is into a big Lan and I had to get a public IP that they have given to me to reach the ip cam over internet.
I tried to set my former DynDns on RouterB but I wasn't able to reach the camera.
I tried to use the public IP through my app phone to reach the camera using the public IP but I couldn't get the camera.
The best result I got was when I used the RouterB as IP Client and I used my public IP into my app phone for camera. On camera status I have OK but video and audio aren't sent..
How can I fix my issue?

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[bob_m_54]

Get the manual, and scroll down to this section.

Configuring Internet Access via Another Router:IP Client



Then see if you have yours set up differently.

[wotnot]

Port forwarding incorrect settings/not set.... at a guess.

[umby75]

@Bob_m_54

I did it. But I was unsure which configuration I had to do.
I chose for a configuration with an existing router but I ignored that my router (the Fritzbox) has a different ip on WAN side and a different one on LAN side and therefore I always did a mess into the configuration.
But now all things work fine and I'm satisfied on my router's features..

@Wotnot

As my reply to Bob_m_54 I wrote my first important issue was the correct configuration from my RouterA that it had to set as modem and I didn't know how I had to do that in practice.
I set for only one ip in assignment range from my RoutersA's dhcp that corresponds to theI IP's RouterB on the WAN side. I enabled the DMZ too in my upstream router (RouterA) for that IP.
Afterwards I set the RouterB with different IPs pool into its LAN and managed the ports with correct and respective MACs and IPs and all work fine!
Many thanks for your help!!!!

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