Cisco 7100 Series Spezifikationen PDF herunterladen (Seite 35)

Intranet VPN Business Scenario 3-5

Step 1—Configuring the Tunnel

Figure 3-3 IP Tunneling Terminology and Concepts

GRE is capable of handling the transportation of multiprotocol and IP multicast trafﬁc

between two sites, which only have IP unicast connectivity. The importance of using

tunnels in a VPN environment is based on the fact that IPSec encryption only works on IP

unicast frames. Tunneling allowsfor the encryption and the transportation of multiprotocol

trafﬁc across the VPN since the tunneled packets appear to the IP network as an IP unicast

frame between the tunnel endpoints. Tunnels also enable the use of private network

addressing across a service provider’s backbone without the need for running the Network

Address Translation (NAT) feature, if all connectivity must go through the home gateway

router.

This section contains basic steps to conﬁgure a GRE tunnel and includes the following

tasks:

1 Conﬁguring the Tunnel Interface, Source, and Destination

2 Verifying the Tunnel Interface, Source, and Destination

802.3 802.2 Payload

PayloadEthernet IP GRE

Normal packet

Tunnel packet

Passenger protocol

Encapsulation protocol

Transport protocol

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Cisco 7100 Series Spezifikationen Seite 35