OTV is a MAC-in-IP method that extends Layer 2 connectivity across a transport network infrastructure. OTV uses MAC address-based routing and IP-encapsulated forwarding across a transport network to provide support for applications that require Layer 2 adjacency, such as clusters and virtualization.
The core principles on which OTV operates are the use of a control protocol to advertise MAC address reachability information (instead of using data plane learning) and packet switching of IP encapsulated Layer 2 traffic (instead of using circuit switching) for data forwarding. These features are a significant departure from the core mechanics of traditional Layer 2 VPNs. In traditional Layer 2 VPNs, a static mesh of circuits is maintained among all devices in the VPN to enable flooding of traffic and source-based learning of MAC addresses. This full mesh of circuits is an unrestricted flood domain on which all traffic is forwarded. Maintaining this full mesh of circuits severely limits the scalability of existing Layer 2 VPN approaches. At the same time, the lack of a control plane limits the extensibility of current Layer 2 VPN solutions to properly address the requirements for extending LANs across data centers.
OTV uses Ethernet over Generic Router Encapsulation (GRE) and adds an OTV shell to the header to encode VLAN information. The OTV encapsulation is 42 bytes. OTV does not require the configuration of pseudo-wires or tunnels. The encapsulation of the packets sent to the overlay is performed dynamically based on a Layer 2 address destination lookup. OTV is supported on Nexus 7000 series all M-series modules. OTV is not supported on F1-series modules.
No effect on existing network design
Failure isolation and site independence
Optimal bandwidth utilization resiliency and scalability
Transparent migration path
Prerequisites for OTV
OTV has the following prerequisites:
OTV has the following configuration guidelines and limitations:
Configure a single join-interface, which is shared across multiple overlays.
Configure a different join interface for each overlay, which increases the OTV reliability.