Corporate Headquarters

3-8
Cisco IOS VPN Configuration Guide
OL-8336-01
Chapter 3 Site-to-Site and Extranet VPN Business Scenarios
Step 1—Configuring the Tunnel
This section contains basic steps to configure a GRE tunnel and includes the following tasks:
•
Configuring the Tunnel Interface, Source, and Destination
•
Verifying the Tunnel Interface, Source, and Destination
Configuring the Tunnel Interface, Source, and Destination
To configure a GRE tunnel between the headquarters and remote office routers, you must configure a 
tunnel interface, source, and destination on the headquarters and remote office routers. To do this, 
complete the following steps starting in global configuration mode.
Note
The following procedure assumes the tunnel interface, source, and destination on the remote office 
router are configured with the values listed in 
Table 3-1
. 
Note
When configuring GRE, you must have only Cisco routers or access servers at both ends of the tunnel 
connection.
Command
Purpose
Step 1
hq-sanjose(config)#
interface tunnel 0
hq-sanjose(config-if)#
ip address 172.17.3.3 
255.255.255.0
Specify a tunnel interface number, enter interface 
configuration mode, and configure an IP address and 
subnet mask on the tunnel interface. This example 
configures IP address and subnet mask 172.17.3.3 
255.255.255.0 for tunnel interface 0 on the headquarters 
router.
Step 2
hq-sanjose(config-if)#
tunnel source 172.17.2.4 
255.255.255.0
Specify the tunnel interface source address and subnet 
mask. This example uses the IP address and subnet mask 
of T3 serial interface 1/0 of the headquarters router.
Step 3
hq-sanjose(config-if)#