In order to fulfill the requirement to prevent the creation of end-to-end loops across a
multihomed OTV network that connects two different data centers, what is the solution to
this problem?
A.
prioritize the transmission of STP BPDUs across the overlay
B.
design the DCI connectivity as a hub and spoke
C.
define a conservative TTL for all packets traversing the OTV network
D.
enable AED on a per-VLAN basis between each OTV edge device with the same site ID
http://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-644634.html
Multipathing and AED
When sites are multihomed, as in the case here, there could be potential for loops to be created between the OTV overlay and the Layer 2 domains at different sites. Unlike other Layer 2 VPN techniques OTV does not use Spanning Tree Protocol on the overlay to break any loops between sites. It has its own loop prevention mechanism, which allows each site to maintain its own Spanning Tree Protocol domain separate from all other sites.
OTV achieves this separation by electing an authoritative edge device (AED) for each VLAN, which is the only device that can forward the traffic for the extended VLAN inside and outside the data center The AED election is based on an internal hash of VLAN ID and number of edge devices in a site. Today the extended VLANs are split in odd and even and automatically assigned to the site’s edge devices. This results in an edge device being the AED for the odd VLANs and the other edge device being the AED for the even VLANs. This assignment is not configurable at this time and is done automatically by NX-OS.