OTV(Overlay Transport Virtualization) is a technology that provide layer2 extension capabilities between different data centers. In its most simplest form OTV is a new DCI (Data Center Interconnect) technology that routes MAC-based information by encapsulating traffic in normal IP packets for transit.
Cisco has submitted the IETF draft but it is not finalized yet. draft-hasmit-otv-01
Traditional L2VPN technologies, like EoMPLS and VPLS, rely heavily on tunnels. Rather than creating stateful tunnels, OTV encapsulates layer2 traffic with an IP header and does not create any fixed tunnels.
OTV only requires IP connectivity between remote data center sites, which allows for the transport infrastructures to be layer2 based, layer3 based, or even label switched. IP connectivity as the base requirement along some additional connectivity requirements that will be covered in this post.
OTV requires no changes to existing data centers to work, but it is currently only supported on the Nexus 7000 series switches with M1-Series linecards.
A big enhancement OTV brings to the DCI realm, is its control plane functionality of advertising MAC reachability information instead of relying on the traditional data plane learning of MAC flooding. OTV refers to this concept as MAC routing, aka, MAC-in-IP routinig. The MAC-in-IP routing is done by encapsulating an ethernet frame in an IP packet before forwarded across the transport IP network. The action of encapsulating the traffic between the OTV devices, creates what is called an overlay between the data center sites. Think of an overlay as a logical multipoint bridged network between the sites.
OTV is deployed on devices at the edge of the data center sites, called OTV Edge Devices. These Edge Devices perform typical layer-2 learning and forwarding functions on their site facing interfaces (the Internal Interfaces) and perform IP-based virtualization functions on their core facing interface (the Join Interface) for traffic that is destined via the logical bridge interface between DC sites (the Overlay Interface).
Each Edge Device must have an IP address which is significant in the core/provider network for reachability, but is not required to have any IGP relationship with the core. This allows OTV to be inserted into any type of network in a much simpler fashion.
Lets look at some OTV terminology.
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