[HELP] How connect two asterisk servers?

I have start to use asterisk from just few mounts and everyting is ok.

Now I need to connect a my asterisk server to another once. For the moment both the server are on my LAN.

The first server have address 192.168.1.3.

The second server it’s at 192.168.1.23. I want that two SIP phone registred on this second server can comunicate passing through the first server (192.168.1.3).

For example:

(SIP phone 260)—>192.168.1.23—>192.168.1.3—>192.168.1.23—>(SIP phone 261)

I understand that I have to modify sip.conf and extension.conf but I don’t know how.

voip-info.org/wiki-Asterisk±+dual+servers

Tank you so much, I think is exactly what I’m searching for.