3Com MSR 50 Series Configuration Manual page 1592

1592 C 81: GRE C
HAPTER ONFIGURATION
Scope enlargement of the network running a hop-limited protocol
Figure 441 Scope enlargement of the network
Router A
IP network
Host A
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.
VPN creation by connecting discontinuous subnets
Figure 442 Connect discontinuous subnets with a tunnel to form a VPN
Novell IPX protocol
In the example as shown in
are deployed in different cities. They can constitute a trans-WAN virtual private
network (VPN) through the tunnel.
GRE-IPSec tunnel application
Figure 443 GRE-IPSec tunnel application
Router A
Corporate
intranet
Working with IPSec, GRE allows data packets like routing protocol, voice, and
video packets to be first encapsulated by GRE and then encrypted by IPSec.
GRE tunnel
Router B
IP network
Group 1
GRE tunnel
Router A
IP network
Figure 442, Group 1 and Group 2 running Novell IPX
Internet
GRE tunnel
IPSec tunnel
Router D
IP network
Router C
Host B
Novell IPX protocol
Group 2
Router B
Router B
Remote office
network