ip address 1.1.1.1 255.255.255.0
tunnel source 172.18.1.1
tunnel destination 172.18.1.2
tunnel sequence-datagrams
tunnel checksum
ip address 1.1.1.2 255.255.255.0
tunnel source 172.18.1.2
tunnel destination 172.18.1.1
tunnel sequence-datagrams
tunnel checksum