The Overlay Transport Virtualization (OTV) Loopback Join interface
feature, for the Cisco Nexus 7000 and Nexus 7700 platforms, adds the capability
of an Overlay using a loopback interface as the Join interface. The Loopback
Join Interface adds a PIM-based control plane, where the Loopback interface has
PIM configured and acts as a first-hop/last-hop multicast router into the
multicast core. This gives the capability for the Loopback Join interface to
have multiple Uplinks into the provider Multicast core.
Prior to Release 8.0(1), OTV supports only one uplink interface to
connect to the core, which is an IGMP host interface. PIM cannot be enabled on
this join-interface. Beginning with Release 8.0(1), PIM routing is supported on
the core uplinks through the loopback interfaces. Therefore, the OTV edge
device behaves as a first hop or last hop multicast router towards the core
device. This enables multiple core uplinks to be operational concurrently for
OTV traffic. The PIM Routing support on uplinks utilizes the dynamic unicast
routing-based convergence on the core network topology changes. This feature
facilitates support for a loopback interface for sourcing OTV traffic; and
therefore, the core physical topology changes does not impact Overlay states,
negating the control place churn for OTV databases. PIM on OTV supports the
loopback join interface loopback configuration under Overlay mode, similar to
the existing join interface. You must configure PIM in Sparse mode on the
loopback interface to use the interface for transmitting and receiving OTV
traffic.
The loopback join-interface is used to facilitate the following:
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to source the OTV traffic from the edge device into the core device.
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to source multicast traffic into the core device, in order to
receive OTV traffic from the core device.
The loopback will be operational irrespective of the physical network
topology changes.
Note |
A physical Layer 3 interface cannot be used with the PIM method as an
OTV join interface.
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The same loopback can be used by multiple Overlays to source their
traffic. For a given Overlay, if the join interface changes to a physical
interface, Ethernet, then the behavior for that Overlay will revert to the
older IGMP-host model.