Cisco N7K-C7010 Configuration Guide - Page 266
GRE Tunnels
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Information About IP Tunnels Chapter 8 Configuring IP Tunnels Send document comments to [email protected] • 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. 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 "Configuring IP Tunnels" section on page 8-4. 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 shows the IP tunnel components for a GRE tunnel. The original passenger protocol packet 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 GRE PDU Original Packet Added Headers Delivery Header GRE Header Original IP Header Original Payload GRE Payload Passenger Protocol Transport Carrier Protocol Protocol 185053 Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x 8-2 OL-23435-03