OTV Terminology

Before learning how OTV control and data planes work, you must understand OTV specific terminology.

Edge Device

The edge device (Figure 1-1) performs OTV functions: it receives the Layer 2 traffic for all VLANs that need to be extended to remote locations and dynamically encapsulates the Ethernet frames into IP packets that are then sent across the transport infrastructure.

Figure 1-1 OTV Edge Device

 

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It is expected that at least two OTV edge devices are deployed at each data center site to improve the resiliency, as discussed more fully in Multi-Homing. #建议每个数据中心要有2个OTV边缘设备。

Finally, the OTV edge device can be positioned in different parts of the data center. The choice depends on the site network topology. Figure 1-1 shows edge device deployment at the aggregation layer.

Internal Interfaces #内部端口，就是接受2层流量，并且这些vlan需要扩展到远端数据中心。在有的文档看到叫site interface.

To perform OTV functionality, the edge device must receive the Layer 2 traffic for all VLANs that need to be extended to remote locations. The Layer 2 interfaces, where the Layer 2 traffic is usually received, are named internal interfaces (Figure 1-2).

Figure 1-2 OTV Internal Interfaces

 

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Internal interfaces are regular Layer 2 interfaces configured as access or trunk ports. Trunk configuration is typical given the need to concurrently extend more than one VLAN across the overlay. There is no need to apply OTV-specific configuration to these interfaces. Also, typical Layer 2 functions (like local switching, spanning-tree operation, data plane learning, and flooding) are performed on the internal interfaces. Figure 1-2 shows Layer 2 trunks that are considered internal interfaces which are usually deployed between the edge devices also.

 

Join Interface   #加入端口，其实就是那些作为igmp 客户端发起加入虚拟overlay组播组请求的端口。

The Join interface (Figure 1-3) is used to source the OTV encapsulated traffic and send it to the Layer 3 domain of the data center network.

Figure 1-3 OTV Join Interface

 

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The Join interface is a Layer 3 entity and with the current NX-OS release can only be defined as a physical interface (or subinterface) or as a logical one (i.e. Layer 3 port channel or Layer 3 port channel subinterface). A single Join interface can be defined and associated with a given OTV overlay. Multiple overlays can also share the same Join interface.

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Note http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNexus OTV 术语  几种不同端口" />Support for loopback interfaces as OTV Join interfaces is planned for a future NX-OS release.

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The Join interface is used by the edge device for different purposes:

•http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNexus OTV 术语  几种不同端口" />"Join" the Overlay network and discover the other remote OTV edge devices.

•http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNexus OTV 术语  几种不同端口" />Form OTV adjacencies with the other OTV edge devices belonging to the same VPN.

•http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNexus OTV 术语  几种不同端口" />Send/receive MAC reachability information.

•http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNexus OTV 术语  几种不同端口" />Send/receive unicast and multicast traffic.

Overlay Interface    #overlay 端口，逻辑overlay 端口 支持组播访问端口，本地跟远端overlay加入相同组播组。

The Overlay interface (Figure 1-4) is a logical multi-access and multicast-capable interface that must be explicitly defined by the user and where the entire OTV configuration is applied.

Figure 1-4 OTV Overlay Interface

 

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Every time the OTV edge device receives a Layer 2 frame destined for a remote data center site, the frame is logically forwarded to the Overlay interface. This instructs the edge device to perform the dynamic OTV encapsulation on the Layer 2 packet and send it to the Join interface toward the routed domain.