Which two statements about OTV are true? (Choose two.)
A.
OTV join interfaces must be physical interfaces.
B.
OTV supports authentication of hello messages and control plane PDUs.
C.
Multicast support in the transport network is a strict requirement to establish OTV adjacencies.
D.
All OTV overlay interfaces must use the same join interface.
E.
OTV forwards and processes spanning-tree BPDUs between sites to ensure a loop-free topology.
F.
OTV propagates MAC address reachability information via the underlying IS-IS control-plane.
Answer: B and F.
– The Join interface is a Layer 3 entity and with the current NX-OS release can only be defined as a physical interface (or subinterface) or as a logical one (i.e. Layer 3 port channel or Layer 3 port channel subinterface). A single Join interface can be defined and associated with a given OTV overlay. Multiple overlays can also share the same Join interface.
-The routing protocol used to implement the OTV control plane is IS-IS. It was selected because it is a standard-based protocol, originally designed with the capability of carrying MAC address information in the TLV.
-From a security perspective, it is possible to leverage the IS-IS HMAC-MD5 authentication feature to add an HMAC-MD5 digest to each OTV control protocol message. The digest allows authentication at the IS-IS protocol level, which prevents unauthorized routing message from being injected into the network routing domain. At the same time, only authenticated devices will be allowed to successfully exchange OTV control protocol messages between them and hence to become part of the same Overlay network
-All OTV edge devices must become “adjacent” to each other from an OTV perspective. This can be achieved in two ways, depending on the nature of the transport network interconnecting the various sites:
•If the transport is multicast enabled, a specific multicast group can be used to exchange the control protocol messages between the OTV edge devices.
•If the transport is not multicast enabled, an alternative deployment model is available where one (or more) OTV edge device can be configured as an “Adjacency Server” to which all other edge devices register and communicates to them the list of devices belonging to a given overlay.
Ref: http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Data_Center/DCI/whitepaper/DCI3_OTV_Intro.pdf