在A、B之间创建隧道
A:
ip tunnel add tun0 mode gre remote IPB local IPA
ip addr add 192.168.0.1/30 dev tun0
ip link set tun0 up
ip route add Bnet1 via 192.168.0.2 dev tun0 src 192.168.0.1
.....
ip route add Bnetn via 192.168.0.2 dev tun0 src 192.168.0.1
B:
ip tunnel add tun0 mode gre remote IPA local IPB
ip addr add 192.168.0.2/30 dev tun0
ip link set tun0 up
ip route add Anet1 via 192.168.0.1 dev tun0 src 192.168.0.2
.....
ip route add Anetn via 192.168.0.1 dev tun0 src 192.168.0.2