GRE tunnel over 2 servers with several IPs

Hello,

I try to make a GRE tunnel from my VPS DigitalOcean which have 2 IP addresses on my server which is at home which is a proxmox server, I would like to use the additional IP of my VPS DigitalOcean on one of my VM Proxmox . But I cannot use the additional IP which is on my VPS DigitalOcean at the other end of the tunnel, ie on my Proxmox server.

Server DigitalOcean network config :

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 52:32:f2:04:5d:df brd ff:ff:ff:ff:ff:ff
    inet 206.189.80.53/20 brd 206.189.95.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet 10.15.0.5/16 brd 10.15.255.255 scope global eth0:1
       valid_lft forever preferred_lft forever
    inet6 fe80::5032:f2ff:fe04:5ddf/64 scope link
       valid_lft forever preferred_lft forever

My Home server ( Proxmox ) network config :

root@pve:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP group default qlen 1000
    link/ether 08:00:27:8e:49:d1 brd ff:ff:ff:ff:ff:ff
3: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 08:00:27:8e:49:d1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.80/24 brd 192.168.1.255 scope global vmbr0
       valid_lft forever preferred_lft forever
    inet6 2a01:cb14:aed:d100:a00:27ff:fe8e:49d1/64 scope global dynamic mngtmpaddr
       valid_lft 1767sec preferred_lft 567sec
    inet6 fe80::a00:27ff:fe8e:49d1/64 scope link
       valid_lft forever preferred_lft forever