User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform Chapter 3
Configuration of GRE
3-2
Delivery Header
(Transport Protocol)
GRE Header
(Encapsulation Protocol)
Payload Packet
(Passenger Protocol)
Figure VPN-3-1 Encapsulated tunnel message format
For example: The format of IPX transmission message encapsulated in IP Tunnel is as
follows:
IP GRE IPX
Passager Protocol
Carrier Protocol or
Encapsulation Protocol
Transport Protocol
Figure VPN-3-2 Format of transmission message in the tunnel.
II. Applicable range
GRE can fulfill the following several services:
1) Multi-protocol local network transmits via single-protocol back bone network.
INTERNET
Novell IPX
Protocol
Group1
IP protocol
Term 1
Novell IPX
Protocol
Group2
IP protocol
Term 2
Tunnel RouterB
B
RouterA
A
Figure VPN-3-3 Multi-protocol local network transmits via single-protocol backbone network
In the above figure, Group1 and Group2 are the local networks running Novell IPX
protocol. Term1 and Term2 is the local network running IP protocol. The tunnel
encapsulated with GRE protocol is adopted between Router A and Router B. Thus
Group1and Group2 can communicate without affecting each other, so are Term1 and
Term 2.
2) Enlarge the operating range of the hop-limited network (e.g. IPX).