Within OTV there are several terms that might be confusing. This is a list of all the terms I’ve encountered so far with an explanation.
- OTV edge device: This is the switch that performs all the OTV operations. Layer 2 frames enter the switch and if they need to be transported over the overlay network they will be encapsulated here and sent out of the join interface. All the OTV configuration is done on these devices (with the possible exception of MTU configuration)
- OTV internal interface: This is the interface on the edge device that points toward the datacenter network. It is a layer 2 interface and it needs to support all the vlans that need to be extended across the overlay network. To be able to do so it must be a (dot1q) trunk port.
- OTV join interface: This is the interface on the edge device that points toward the routed network that carries the data toward the other datacenters.
- OTV overlay interface: A logical interface on the edge device. A large part of the OTV configuration is done on this interface. It ensures the encapsulation of the layer 2 frames into layer 3 packets.
- Transport network: This is the IP network that will carry the encapsulated layer 2 frames across to the other datacenter(s). The only requirement to this network is that it needs to be an IP network. It must also support jumboframes or you need to reduce the MTU in your network to ensure the additional overhead of OTV does not cause any problems (OTV does not support fragmentation)
- Overlay network: The logical network that connects OTV devices.
- Site: Most often a datacenter, but nothing prevents you from connecting a campus to a OTV network, so it might be a campus as well.
- Site vlan: The vlan used by OTV edge devices within a site to communicate. This vlan must not be extended across the transport network. All OTV edge devices within a site need to agree on the site vlan. Because the vlan is not extended you could in theory use the same vlan on all sites.
- Authoritative Edge Device: When using multiple OTV edge devices an AED is required. This is the device responsible for forwarding the data on a specific vlan. An AED is configured per vlan, so when using two OTV edge devices you can use both actively but for different vlans. (Only one Edge device is allowed to forward traffic for a specific vlan because of the removal of BPDU’s. If both devices were to forward traffic this might cause loops or MAC flapping.)
- Site-ID: An identifier for the site that all Edge devices in that site must agree upon.
- OTV Shim: OTV specific header which is added to the OTV encapsulated data to clarify among others the vlan from which the frame originated (and must be restored to)
I might encounter other OTV specific terms, and if I do I will list them here.