3Com 10014299 manual Enlarge network operating range

GRE Protocol Overview 637

GRE Services GRE can fulfill the following services:

1Implement the LAN protocol communication in WAN by encapsulating all kinds of LAN protocols into a WAN protocol.

Figure 201 Multi-protocol local network transmitting via single-protocol backbone network

Novell IPX

Group1

Internet

Novell IPX

Group2

IP	Router A Tunnel	Router B
		IP
Term 1		Term 2

In Figure 201, Group1 and Group2 are the local networks running the Novell IPX protocol. Term1 and Term2 is the local network running the IP protocol. The tunnel encapsulated by the GRE protocol is created between Router A and Router B. Thus Group1 and Group2 can communicate without affecting each other, as can Term1 and Term2.

2Enlarge the operating range of the hop-limited network, such as IPX.

Figure 202 Enlarge network operating range

Router	Tunnel	Router
IP network		IP network
Router	IP network	Router
PC		PC

When using RIP, if the hop count between two terminals in Figure 202 is more than 15, the two terminals cannot communicate with each other. If tunneling is used in the network, hop counts will not be incremented inside the tunnel, that is, hops can be hidden, which enlarges the operating range of the network.

3Connect some discontinuous sub-networks to establish a VPN.

Figure 203 Tunnel connecting discontinuous sub-networks

RouterRouter

novell

IP network

novel

l

group 1 VLAN group2

Tunnel