Advantages And Disadvantages Of Gre - HP 7102dl - ProCurve Secure Router Configuration Manual

For example, on the ProCurve Secure Router, a GRE tunnel can:
transit multicast routing protocols, such as Routing Information Protocol
(RIP) and Open Shortest Path First (OSPF), through the Internet
transit any multicast messages, such as those for a video stream
transit traffic through a network that uses the same IP addresses (useful
for integrating sites that use overlapping addresses)
GRE is often used in conjunction with IPSec. It allows two sites to tunnel
routing updates and other multicasts to each other through the Internet.
You can also use GRE to establish a virtual point-to-point tunnel between two
routers separated by an intervening network. For example, you can create a
VPN connection through the Internet between two remote sites. You would
create a tunnel whose address is on the private network, but whose source
and destination endpoints are on the public network.

Advantages and Disadvantages of GRE

Because GRE can encapsulate any protocol that Ethernet can, you can use
GRE to send many types traffic from one point to another. GRE connects far-
flung private routers together as if the intervening hops did not exist.
However, GRE tunnels are not as secure as a tunnel established using IPSec.
The GRE tunnel does not authenticate or encrypt traffic. When you use IPSec
with Internet Key Exchange (IKE) to establish a VPN tunnel, IKE negotiates
the keys that define that tunnel. The keys are dynamic and robust. When you
use GRE, you must define the tunnel yourself, which also renders a GRE tunnel
less secure than an IPSec tunnel.
Because you manually define the tunnel, GRE tunneling is less scalable that
IPSec tunneling. You must create a new tunnel for every point-to-point con-
nection that you want to establish in the VPN.
Like tunneling with IPSec, GRE can tax processing power. However, because
traffic is not encrypted, GRE consumes fewer resources than IPSec.
Configuring a Tunnel with Generic Routing Encapsulation
Overview
11-3