|-----CNGI INTERNET (IPv6)
mobile users----GGSN======NE40-8------INTERNET (IPv4)
1. Realize NAT network address translation in IPv4 network. Change private network address of mobile users under GGSN as public network address on NE40-8. Mobile users can access Internet.
2. In IPv6 network NE40-8 and GGSN establish gre-tunnel based on IPv4. Encapsulate data packet of IPv6 in data domain of IPv4 packet. It is transmitted to GGSN through GRE-Tunnel. GGSN deletes IPv4 encapsulation and sends IPv6 data to mobile users. Mobile users can access IPv6-Internet.
3. GGSN at mobile users can support IPv6 protocol. But GGSN at connection NE40-8 side cannot support IPv6 protocol. It only supports GRE-Tunnel to realize IPv6 data forwarding.
GRE-Tunnel between NE40-8 and GGSN can be established, but the service is unreachable. Mirror and capture packet at NE40-8 tunnel port. It can receive packet sent by opposite tunnel, but it does not send packet to the opposite.
Configure IPv6 address at tunnel interface. IPv6 is made GRE encapsulation and downlinks to GGSN through the tunnel. The problem is solved.
1. NE40-8 can ping through opposite IP address. The tunnel is successfully established.
2. NE40-8 can ping through IP address of interconnected port of uplink device. Uplink is normal.
3. Check routing table and configure the route from downlink to GRE-Tunnel.
4. At NE40-8 tunnel ingress IPv6 is not encapsulated in GRE-Tunnel and forwarded.
Forward IPv6 packet through GRE-Tunnel on NE40. Configure IPv6 address at tunnel interface. Downlink packet of IPv6 can reach the opposite through the tunnel.