when should i use GRE?

[hanyawad]

Hi,

in which situation should i use GRE? is it a replacement or extension of VPN feature?

and is there any document explaining how to configure GRE?

thanks

Labib

[Jon Marshall · Accepted solution]

Labib

GRE has a number of main uses -

1) in conjunction with PPTP to create a L2 PPTP VPN tunnel

2) in conjunction with IPSEC to allow dynamic routing protocols to be carried across the tunnel ie. IPSEC alone does not support the multicast updates that dynamic routing protocols such as EIGRP/OSPF use.

3) to carry non IP traffic eg. if you needed to send IPX data across an IP network

4) as a general tunneling protocol ie. if you wanted to transport some data across an IP network but only allow it to enter and exit the IP network at a certain point. Be aware though, when used this way, you do not have visibility of the data within the GRE tunnel.

For config examples see this link -

http://www.cisco.com/en/US/tech/tk827/tk369/tech_configuration_examples_list.html

Jon

[hanyawad]

thanks alot jon for your clear explaination

labib