H3C Technologies H3C SecPath F1000-E - Manual (Page 29)

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The output information indicates that on Device A there was a tunnel entry to the branch network, and
packets to the branch network were forwarded through Device A.
# On Device C, shutdown interface Tunnel 0 to cut off the tunnel link between Device A and Device C.
[DeviceC] interface tunnel 0
[DeviceC-Tunnel0] shutdown
# After the tunnel entry aging time (20 seconds in this example) elapses, view the tunnel entry
information on Device A.
[DeviceA] display gre p2mp tunnel-table interface tunnel 0
Dest Addr Mask Tunnel Dest Addr Gre Key
# Ping Host A from Host C. The ping operation succeeds. View tunnel entries on Device B and the output
information is as follows:
[DeviceB] display gre p2mp tunnel-table interface tunnel 0
Dest Addr Mask Tunnel Dest Addr Gre Key
192.168.12.0 255.255.255.0 11.1.1.3
The output information indicates that:
• After the link between Device A and Device C went down, the tunnel entry aging timer started to
work.
• After the timer expired, the tunnel entry on Device A was removed.
• After Device C sent a packet to Device B, a tunnel entry to the branch network was generated on
Device B. Packets from the headquarters to the branch network are delivered by Device A to Device
B through the backup interface, and then Device B forwards these packets to the branch.
Configuration Example for P2MP GRE Tunnel Backup at a
Branch
Network requirements
As shown in Figure 17 , a branch uses two gateways at the egress of the internal network, with Device C
for backup. A P2MP GRE tunnel is created on Device A, the gateway at the headquarters, allowing
Device A to establish two GRE tunnels to the branch network, one for connecting Device B and the other
for connecting Device C. Device A decides which GRE tunnel to use to send packets to the hosts on the
branch network.
To meet the above requirements, you need to configure different GRE keys for the GRE tunnels on Device
B and Device C, so that Device A can choose a tunnel according to the GRE key values.
In this example, the GRE tunnel between Device A and Device B has a higher priority.