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. It encapsulates Layer 2 frames in IP unicast or multicast headers.Įvery 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.
Overlay interface: This is a logical multiaccess multicast-capable interface. Send/receive unicast and multicast traffic. Send/receive MAC reachability information. “Join” the overlay network and discover the other remote OTV edge devices.įorm OTV adjacencies with the other OTV edge devices belonging to the same VPN. The join interface is used by the edge device for different purposes: Join interface: This is the 元 interface of the ED that faces the core. Typical Layer 2 functions (like local switching, spanning tree operation, data plane learning, and flooding) are performed on the internal interfaces. There is no need to apply OTV-specific configuration to these interfaces. Trunk configuration will extend more than one VLAN across the overlay. Internal interfaces are regular access or trunk ports. Internal interfaces: These are the L2 interfaces (usually 802.1q trunks) of the ED that face the site. To understand how OTV works in an existing IP transport environment, let’s discuss the OTV interfaces and terms shown in Figure 3-1.Įdge device (ED): This device connects the site to the (WAN/MAN) core and is responsible for performing all the OTV functions.Īn edge device receives 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 OTV transport infrastructure.įor resiliency, two OTV edge devices can be deployed on each site to provide redundancy. This is achieved by leveraging the same control plane protocol used for the exchange of MAC address information, without the need of extending the Spanning Tree Protocol (STP) across the overlay. Two or more devices can be leveraged in each data center to provide LAN extension functionality without running the risk of creating an end-to-end loop that would jeopardize the overall stability of the design.
OTV provides a native built-in multihoming capability with automatic detection. Immediate advantages include improved flexibility when adding or removing sites to the overlay, more optimal bandwidth utilization across the WAN (specifically when the transport infrastructure is multicast enabled), and independence from the transport characteristics (Layer 1, Layer 2, or Layer 3). This eliminates the need to establish virtual circuits, called pseudowires, between the data center locations. Each Ethernet frame is individually encapsulated into an IP packet and delivered across the transport network. OTV also introduces the concept of the dynamic encapsulation for Layer 2 flows that need to be sent to remote locations. If the destination MAC address information is unknown, traffic is dropped (not flooded), preventing the waste of precious bandwidth across the WAN. As outlined in this chapter, Layer 2 communication between sites resembles routing more than switching. This is a significant shift from Layer 2 switching that traditionally leverages data plane learning, and it is justified by the need to limit flooding of Layer 2 traffic across the transport infrastructure. Overlay transportation introduces the concept of “MAC routing,” which means a control plane protocol is used to exchange MAC reachability information between network devices providing LAN extension functionality.
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