Chapter8 Site-to-Site VPN
Create Site to Site VPN
8-48
Cisco Router and Security Device Manager Version 2.2 User’s Guide
OL-4015-08
•The hash, encryption, DH group, and Authentication Type of the IKE policies
that the hub uses, so that compatible IKE policies can be configured on the
spoke.
•The ESP and Mode information of the transform sets that the hub uses. If
similar transform sets have not been configured on the spoke, they can be
configured using this information.
Secure GRE Tunnel (GRE-over-IPSec)
Generic routing encapsulation (GRE) is a tunneling protocol developed by Cisco
that can encapsulate a wide variety of protocol packet types inside IP tunnels,
creating a virtual point-to-point link to Cisco routers at remote points over an IP
internetwork. By connecting multiprotocol subnetworks in a single-protocol
backbone environment, IP tunneling using GRE allows network expansion across
a single-protocol backbone environment.
This wizard enables you to create a GRE tunnel with IPSec encryption. When you
create a GRE tunnel configuration, you also create an IPSec rule that describes the
endpoints of the tunnel.
GRE Tunnel Information
General GRE tunnel information is provided in this screen.

Tunnel Source

Select the interface name or the IP address of the interface that the tunnel will use.
The IP address of the interface must be reachable from the other end of the tunnel;
therefore it must a a public, routable IP address. An error will be generated if you
enter an IP address that is not associated with any configured interface.
Note SDM lists interfaces with static IP addresses and interfaces configured as unnumbered
in the Interface list. Loopback interfaces are not included in the list.