H3C Technologies H3C S12500 Series Switches - Manual (Page 188)

175
429B
Connecting private networks running different protocols over a single backbone
Figure 74 Network diagram
As shown in
813H
Figure 74 , Group 1 and Group 2 are IPv6 networks, and Team 1 and Team 2 are IPv4
networks. Through the GRE tunnel between Device A and Device B, Group 1 can communicate with
Group 2 and Team 1 can communicate with Team 2, without affecting each other.
430B
Enlarging network scope
Figure 75 Network diagram
In an IP network, the maximum TTL value of a packet is 255. If two devices have more than 255 hops in
between, they cannot communicate with each other. By using a GRE tunnel, you can hide some hops to
enlarge the network scope. As shown in
814H
Figure 75 , only the tunnel-end devices (Device A and Device D)
of the GRE tunnel are counted in hop count calculation. Therefore, there are only three hops between
Host A and Host B.
IPv6 protocol
Group 1
Internet
IP protocol
Team 1
IPv6 protocol
Group 2
IP protocol
Team 2
Device A Device B
GRE tunnel
Device A
Device B Device C
Device D
Host A Host B
IP network
GRE tunnel
IP network
IP network