Transparent cascading proxy with another parent proxy

[omaralonso]

Hello everyone ! I hope someone can guide me.
My situation is as follows:
I have installed version 17.7 of OpnSense and I would like to use a transparent proxy + captive portal, but my problem is that the access to my internet is by proxy and I do not know how to do so that all the requests of my transparent proxy finally reach my parent proxy (The one offered by my internet provider), that is: my transparent proxy has to be synchronized with the other proxy (the parent) so that you finally have access to the internet from the transparent proxy without having to manually configure any proxy.
I'm not sure how they call this in technical language:
Cascading proxy
Forwarding proxy
Outbound proxy
Streaming proxy
Parent proxy

I dont know !
I searched the settings of OpnSense and found nothing that would allow me to do what I want.
My parent proxy is for example http://192.168.20.1:3128 and my transparent proxy is http://192.168.2.1:3128
Is it possible that no one in the world accesses the internet through an HTTP proxy, or is it only OpnSense users who do not use it?
Well any answer I will deeply appreciate it.
Thank you and have a good day.

[fabian]

You need to have this option in the proxy settings:
http://www.squid-cache.org/Doc/config/cache_peer/

BTW: In my opinion you should change your ISP as you should get a (dynamic) public IP to the internet or at least private IP without the requirement of a proxy with the option to get a (dynamic) public IP.

[omaralonso]

Thanks for replying fabian.
Unfortunately I can not access the Internet in any other way, I have to use a proxy. For these reasons it is that I need to find a way to do this to have access to the Internet and that my opnsense can be updated. I'm going to study this that you recommend me and then I'll tell you what the result was. All this I can do without the need to add additional packages? Is there any tutorial or video how to do this? Is that because you tell me that can not be done from the GUI, I do not want to destroy my opnsense with some mistake on my part. Thanks and regards