R3166-R3206-HP High-End Firewalls VPN Configuration Guide-6PW101

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GRE applications
Multi-protocol communications through a single-protocol backbone
Figure 4 Multi-protocol communications through a single-protocol backbone
In the example shown in Figure 4, Group 1 and Group 2 are local networks running Novell IPX, and
Team 1 and Team 2 are local networks running IP. Through the GRE tunnel between Device A and Device,
Group 1 can communicate with Group 2 and Team 1 can communicate with Team 2. They will not
interfere with each other.
Scope enlargement of a hop-limited protocol such as RIP
Figure 5 Network scope enlargement
When the hop count between two terminals exceeds 15, the terminals cannot communicate with each
other. Using GRE, you can hide some hops so as to enlarge the scope of the network.
Novell IPX protocol
Group 1
Internet
IP protocol
Team 1
Novell IPX protocol
Group 2
IP protocol
Team 2
Device A Device B
GRE tunnel