How to set up a GRE tunnel on CentOS7 - Debian 10?

Question

linux

Hello, I am preparing for worldskills according to a certain book, the screenshots contain my setup, as well as the output of information by the ip a command on both machines (L-FW - CentOS, R-FW - Debian)

I made a bash script that creates an interface on startup this machine(L-FW) (R-FW)

Then made it executable: chmod +x /etc/gre.up (L-FW) (R-FW)
Added script to autoload via Crontab( R-FW)
Added script to autoload in the file /etc/network/interfaces (wrote the line post-up /etc/gre.up)(L-FW)

When I try to execute the ping command, something happens:

Please tell me, what is my mistake?