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Cisco Router and Security Device Manager Version 2.2 User’s Guide
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Chapter8 Site-to-Site VPN
Create Site to Site VPN
Backup GRE Tunnel Information
You can configure a backup GRE-over-IPSec tunnel that the router can use when
the primary tunnel fails. This tunnel will use the same interface that you
configured for the primary tunnel, but it must be configured with the backup VPN
router as the peer. If routing is configured for the primary GRE-over-IPSec tunnel,
the keepalive packets that the routing protocol sends are used to verify that the
tunnel is still active. If the router stops receiving keepalive packets on the primary
tunnel, then traffic is sent through the backup tunnel.

Create a backup secure GRE tunnel for resilience

Check this box if you want to create a backup tunnel.

IP address of the backup GRE tunnel’s destination

Enter the IP address of the interface on the remote router at the other end of the
tunnel. (This is the source interface from the point of view of the other end of the
tunnel.)
Make sure that this address is reachable by using the ping command. The ping
command is available from the Tools menu. If the destination address specified in
the Ping dialog cannot be reached, the tunnel will not be created properly.

Tunnel IP address

Enter the IP address of the tunnel. The IP addresses of b oth ends of the tunnel
must be in the same subnet. The tunnel is given a separate IP address so that it can
be a private address, if necessary.
IP Address
Enter the IP address of the tunnel in dotted decimal format. For more information,
see IP Addresses and Subnet Masks.
Subnet Mask
Enter the subnet mask for the tunnel address in dotted decimal format.