How to set up the GRE Tunnel correctly?

Question

VPN

Hello.
Tell me how to correctly configure the GRE tunnel.
Thoughts began to get confused.
It is necessary that the tunnel connects only two servers (Asterisk).
Now it connects completely two networks.
I can only change the settings in Moscow, Peter is not in my competence.
It is necessary that the server with IP 192.1.10.10 can see the server with IP 168.1.20.20 and nothing more.
Source:
IP Moscow - XXXX
IP Peter - YYYY
Tunnel Moscow - 10.20.1.1 255.255.255.252
Tunnel Peter - 10.20.1.2 255.255.255.252
Moscow network - 192.1.0.0/16
Peter network - 168.1.0.0/16
Setting Moscow
interface Tunnel0
ip address 10.20.1.1 255.255.255.252
shutdown
tunnel source XXXX
tunnel destination YYYY
ip route 168.1.0.0 255.255.0.0 10.20.1.2
Thanks for your help

Answer 1

so you ip route 168.1.0.0 255.255.0.0 10.20.1.2 you have a mask of 16 for the entire subnet. Specify explicitly
ip route 168.1.20.20 255.255.255.255 10.20.1.2