Hello Zulqurnain,

since a tunnel is just a virtual pipe for transferring data, the actual speed depends on the physical capacity of the underlying connection. Let's say you have an E1 leased line between two routers, and you build a tunnel between the routers, the speed would be the same as the E1.

When you create the tunnel interface, the output of 'show interface tunnel' actually says ' bandwidth 9 Kbit', but this is just an arbitrary value.

There is an article on VPNs in the latest Packet Magazine issue, which you might find useful to read, here is the link:

The ABCs of VPNs

http://www.nxtbook.com/nxtbooks/cisco/packet-2q-06/index.php?startpage=16

Also, the technical documentation pages on CCO contain information about various tunneling techniques (IPSec/VPN/GRE etc.), have a look at the link below:

http://www.cisco.com/en/US/tech/tk583/tsd_technology_support_category_home.html

Regards,

GNT