OTV Failure isolation
One of the main requirements of every LAN extension solution is to provide Layer 2 connectivity between remote sites without giving up the advantages of resiliency, stability, scalability, and so on, obtained by interconnecting sites through a routed transport infrastructure.
OTV achieves this goal by providing four main functions:
- Spanning Tree (STP) isolation
- Unknown Unicast traffic suppression
- ARP optimization
- Broadcast policy control.
STP Isolation
The figure below shows how OTV, by default, does not transmit STP Bridge Protocol Data Units (BPDUs) across the overlay. This is a native function that does not require the use of an explicit configuration, such as BPDU filtering, and so on. This allows every site to become an independent STP domain: STP root configuration, parameters, and the STP protocol flavor can be decided on a per-site basis.
This fundamentally limits the fate sharing between data center sites: an STP problem in the control plane of a given site would not produce any effect on the remote data centers.
Limiting the extension of STP across the transport infrastructure potentially creates undetected end-to-end loops that would occur when at least two OTV edge devices are deployed in each site, inviting a common best practice to increase resiliency of the overall solution. Multi-Homing details how OTV prevents the creation of end-to-end loops without sending STP frames across the OTV overlay.
