Chapter 8 Configuring Ip Tunnel; Gre Tunnels - Cisco 7206 - VXR Router Configuration Manual

Information About IP Tunnels
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m
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An IP tunnel takes a passenger protocol, such as IPv4, and encapsulates that protocol within a carrier
protocol, such as GRE. The device then transmits this carrier protocol over a transport protocol, such as
IPv4.
You configure a tunnel interface with matching characteristics on each end of the tunnel.
For more information, see the
You must enable the tunnel feature before you can see configure it. Beginning in Cisco NX-OS Release
4.2, the system automatically takes a checkpoint prior to disabling the feature, and you can roll back to
this checkpoint. See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide,
Release 5.x, for information on roll backs and checkpoints.
Beginning with Cisco NX-OS Release 4.2, a tunnel configured in one VDC is isolated from a tunnel with
the same number configured in another VDC. For example, Tunnel 0 in VDC 1 is independent of tunnel
0 in VDC 2.
Beginning with Cisco NX-OS Release 4.2, your tunnel source IP address and destination IP address
should be in the same VRF.

GRE Tunnels

Note Beginning with Cisco NX-OS Release 5.1(1), the software supports multicasting over GRE tunnels.
You can use generic routing encapsulation (GRE) as the carrier protocol for a variety of passenger
protocols.
Figure 8-1
becomes the GRE payload and the device adds a GRE header to the packet. The device then adds the
transport protocol header to the packet and transmits it.
Figure 8-1
Delivery
Transport
Protocol
Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x
8-2
Passenger protocol—The protocol that needs to be encapsulated. IPv4 is an example of a passenger
protocol.
Carrier protocol—The protocol that is used to encapsulate the passenger protocol. Cisco NX-OS
supports GRE as a carrier protocol.
Transport protocol—The protocol that is used to carry the encapsulated protocol. IPv4 is an example
of a transport protocol.
shows the IP tunnel components for a GRE tunnel. The original passenger protocol packet
GRE PDU
Original IP
Original Packet
Header
Added Headers
GRE
Header
Header
Carrier
Protocol
"Configuring IP Tunnels" section on page
Original Payload
GRE Payload
Chapter 8 Configuring IP Tunnels
8-4.
Passenger
Protocol
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