Digital Building Ring Topology: Protocols for Resilience | Cisco CCIE Service Provider Exam

Protocols for Resilience in a Digital Building Ring Topology

Question

Which two protocols can be used for resilience in a Digital Building Ring topology?

Answers

Explanations

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A. B. C. D. E.

CE.

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-digital-building-series-switches/guide-c07-740588.html

Digital Building Ring (DBR) is a network topology commonly used in building automation and control systems (BACS) to provide high availability and redundancy. In a DBR, devices are connected in a ring topology, and data flows in both clockwise and counterclockwise directions. To ensure resilience and fast convergence in case of link or node failures, protocols that support ring topologies and provide fast convergence are required.

Out of the protocols listed in the question, two protocols that can be used for resilience in a Digital Building Ring topology are:

  1. REP (Resilient Ethernet Protocol)
  2. STP (Spanning Tree Protocol)

Explanation:

  1. REP (Resilient Ethernet Protocol): REP is a Cisco proprietary protocol that is used to provide sub-50 ms convergence in ring topologies. REP can detect and respond to link failures in a ring topology by rerouting traffic in the opposite direction of the failure. REP uses a token-passing mechanism to prevent loops and ensure that only one node can transmit at a time. In a DBR, REP can be used to provide fast convergence and redundancy.

  2. STP (Spanning Tree Protocol): STP is a widely used protocol that provides redundancy and loop prevention in switched networks. STP can be used in a DBR to prevent loops and provide redundancy. However, STP can have slow convergence times, which can be problematic in large networks. To overcome this limitation, Rapid Spanning Tree Protocol (RSTP) or Multiple Spanning Tree Protocol (MSTP) can be used instead of STP.

The other protocols listed in the question are not suitable for resilience in a Digital Building Ring topology:

  • IS-IS (Intermediate System to Intermediate System) is a routing protocol that is used in large networks. IS-IS is not designed for ring topologies and may not be suitable for building automation networks.
  • LLDP (Link Layer Discovery Protocol) and CDP ( Cisco Discovery Protocol) are protocols used for network discovery and device identification. They do not provide resilience or redundancy in a network.

In summary, REP and STP are the two protocols that can be used for resilience in a Digital Building Ring topology. REP provides fast convergence and redundancy, while STP provides redundancy and loop prevention.