# >> Continuing Education >> Be Self Taught

How to Configure GRE Tunnels

Although now standard, Cisco originally developed the Generic Routing Encapsulation (GRE) protocol. GRE tunnels allow network administrators to transport packets from one network to another. The protocol forms the basis for many other tunneling protocols, such as the point-to-point tunneling protocol (PPTP) that Microsoft Virtual Private Networking (VPN) uses. Learning how to configure GRE tunnels allows you to exercise greater control over connecting multiple networks.

Instructions

- 1
  Open the router interface for the first router. Follow the manufacturer's instructions for accessing the interface.
- 2
  Type "interface Ethernet0/1 IP address 10.2.2.1 255.255.255.0 interface Serial0/0 IP address 192.168.4.1 255.255.255.0 interface Tunnel0 IP address 1.1.1.2 255.255.255.0 tunnel source Serial0/0 tunnel destination 192.168.4.2" (without the quotation marks) in the interface for the first router. Replace the IP addresses beginning "192" with the IP addresses for your routers.
- 3
  Open the router interface for the second router.
- 4
  Enter "interface FastEthernet0/1 IP address 10.1.1.1 255.255.255.0 interface Serial0/0 IP address 192.168.4.2 255.255.255.0 interface Tunnel0 IP address 1.1.1.1 255.255.255.0 tunnel source Serial0/0 tunnel destination 192.168.4.1" (without quotation marks) in the second router's interface. Replace the IP addresses beginning "192" with the IP addresses for the two routers. Make sure that the line "tunnel destination" lists the IP address for the other router.

How to Determine the Climates of the Past

Roland TD-3 Vs. Roland TD6

Be Self Taught