• Author : ASHWIN C S

 
 

PTP Best Master Clock Algorithm (BMCA)

Scope This article describes the “Best Master Clock Algorithm”(BMCA) and the manner in which it’s carried out on Arista switches. BMCA BMCA is used for selecting a Grandmaster (GM) in a PTP domain. Additionally, it is also used to decide the PTP port-states on the Arista switches. PTP port-states Master It provides timing to a downstream clock. PTP master ports send out announce messages. Slave It retrieves timing from an upstream clock. In this state, the port doesn’t send out announce messages. Passive A backup slave port. This state prevents timing loops. There are no announce messages sent out of...
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PTP slave-passive port election

Scope 1. This article takes account of how the slave-passive port election for PTP is done on Arista switches. Slave-Passive port election order The below sequence of comparison occurs in order to decide if a port should take slave or passive state: 1. Steps removed 2. Parent clock identity 3. Self Port-ID Steps removed “Steps removed” is the number of hops separating a PTP clock from the GM. The port that has a lower “steps removed” value is preferred as a slave port. The grandmaster in a PTP domain has a “steps removed” value equivalent to zero. Every subsequent PTP running port in...
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“Wait-for-warmup” command – To understand if an agent has initialized

Objective The aim of this document is to convey the use case and details of the bash command, wait-for-warmup (wfw). An equivalent CLI command exists for the same which is described later in this article. Main use case Agents like the forwarding agent of the switch take some time to come up when terminated. The same is the case for the linecard and fabric module agents when the fabric modules/linecards are power-cycled. It’d be useful to run the wfw command to check if the agent has initialized completely instead of running other commands repeatedly to check the same. (If interfaces...
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Basic troubleshooting steps for some CVP and telemetry issues

Objective The aim of this document is to convey a set of troubleshooting steps that can be carried out when running into issues with CVP and telemetry. General issues covered Issue 1- The CVP web-explorer is not reachable Issue 2- A configlet/image bundle push task to the switch failed Issue 3- Device not getting added to telemetry 1. The CVP web-explorer is not reachable Follow the below sequential steps in order to isolate the issue: 1. Check if the CVP node is reachable from the local machine. 2. Login to the CVP node as a CVP user and check if...
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