Cisco Cisco IOS Software Releases 12.2 MC Livre blanc

 shows a sample topology for site-to-site configuration of IPSec Stateful Failover with generic 

routing encapsulation (GRE), a tunnel interface not tied to specific “passenger” or “transport” protocols. 
GRE supports multicast traffic, critical for V3PN applications.

There are four possible configurations for the Cisco 7200 series routers using Cisco IOS 
Release 12.2(14)SU, 12.2(14)SU1, or 12.2(14)SU2:

non-GRE High Availability (HA) with a virtual IP (VIP), or redundancy groups, on the outside and 
a VIP on the inside (see 

non-GRE HA with only VIPs on the outside. The route to the outside is provided by Reverse Route 
Injection (RRI) (see 

GRE HA, with VIPs on the outside and tested inside faces (see 

GRE HA, with only a VIP on the outside, using RRI to inject routes (see 

Remote Peer 1

Internet

Headquarters

(Private Network)

Remote Peer N

97371

Standby

Head-End

Router

Head-End

Router

VIP

(shared IP

address)

GRE Tunnel 1

GRE Tunnel N

114186

Head-End

A

S

Outside

VIP

Inside

VIP

Remote LAN

Peer

Private LAN

Inside VIP configured as default gateway

for route from private LAN to remote LAN