Tunnel Gre problem between two hosts (vps and dedicated server)

[AleDevite]

Hello guys i need to resolve this problem (all server have installed centos 7): i'm trying to create a gre tunnel through vps (in Italy - OpenVZ)
and a dedicated server (in Germany), but they do not communicate internally (ping and ssh command tests).
Next i create a gre tunnel trought vps (in Italy - OpenVZ) and vps (in France - KVM OpenStack) and their communicate, i next i had create a tunnel trought vps (in France - KVM OpenStack) and a dedicated server (in Germany) their communicate.
I can not understand why the vps (in Italy - OpenVZ) and the dedicated server (in Germany) do not communicate,
ideas on how I can fix (I also tried with iptables disabled, firewalld is not enable)? Thanks

1. VPS command for tunnel:

•       echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
        iptunnel add gre1 mode gre local VPS_IP remote DEDICATED_SERVER_IP ttl 255
        ip addr add 192.168.168.1/30 dev gre1 ip link set gre1 up

2. Dedicated server command for tunnel:

•       iptunnel add gre1 mode gre local DEDICATED_SERVER_IP remote VPS_IP ttl 255
        ip addr add 192.168.168.2/30 dev gre1
        ip link set gre1 up

[root@VPS ~]# ping 192.168.168.2
PING 192.168.168.2 (192.168.168.2) 56(84) bytes of data.
^C
--- 192.168.168.2 ping statistics ---
89 packets transmitted, 0 received, 100% packet loss, time 87999ms

[root@DE ~]# ping 192.168.168.1
PING 192.168.168.1 (192.168.168.1) 56(84) bytes of data.
^C
--- 192.168.168.1 ping statistics ---
92 packets transmitted, 0 received, 100% packet loss, time 91001ms

[root@VPS ~]# lsmod | grep gre
ip_gre                  4242  -2
ip_tunnel              4242  -2 sit,ip_gre
gre                    4242  -2 ip_gre


[root@DE ~]# lsmod | grep gre
ip_gre                22707  0
ip_tunnel              25163  1 ip_gre
gre                    13144  1 ip_gre