H3C Technologies H3C SecPath F1000-E - Manual (Page 19)

3
P2MP GRE Tunnel Backup
GRE tunnel backup at a branch
Figure 13 GRE tunnel backup at a branch
Device B
Device C
(Backup gateway)
IPv4 network
Device A
Tunnel0
Tunnel0
Tunnel0
Host B
Host A
Headquarters
Branch
GRE P2MP tunnel
As shown in
Figure 13 , for higher network reliability, a branch can use multiple gateway devices so that
a GRE tunnel is established between the headquarters and each gateway of the branch for GRE tunnel
backup.
When creating a GRE tunnel on a gateway of the branch, you can configure the GRE key. The device at
the headquarters will read the GRE key from the GRE packet and record the GRE key value in the
corresponding tunnel entry. The device at the headquarters determines the priority of a tunnel entry
according to the value of the GRE key, and uses the tunnel corresponding to the tunnel entry with the
highest priority to forward packets destined for the peer and uses the other tunnels for backup. A tunnel
entry without a GRE key has the highest priority. For tunnel entries carrying a GRE key, a smaller key
value means a higher priority.
NOTE:
You can configure the GRE key on only a tunnel interface in P2P GRE tunnel mode. A tunnel interface
working in P2MP GRE tunnel mode does not support the GRE key argument.