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PFRv3 channel state questions

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This document gives several answers on frequently asked questions for PFRv3 channel state behavior.

Q1: What are all the channel operational states from a BR (border role) perspective and what are the rules/conditions to be in each state?

A1: Channel state machine from border perspective:

Overview

In PfRv3, border channel has the following three stats:

  • Provisional State: to indicate whether there's TC relying on this group on Channel <DSCP, Peer-Site-ID, Any-WAN-Exit>.
  • RX State: detected by local data plane to indicate the Channel reachability from remote to local.
  • TX State: detected by remote site, sending to local MC by unreachable TCA.

 

Rx state:

Rx.png

 Tx state:

Tx.png

 

Q2: What are all the channel operational states from a master perspective and what are the rules/conditions to be in each state?

A2: Channel state machine from a master perspective:

In PfRv3, master channel has the following three stats:

  • Not-available (Initial state);
  • Not-available (no next-hop);
  • Available;
  • Available, but unreachable.

MC.jpg

 

Q3: What are the channel states for Internet channels (site-id 255.255.255.255)?

A3: Channel states differ from the states for regular channels:

Channel Provisional State Machine:

I1.png

Channel Rx State Machine:

I2.png

Channel Tx State Machine:

I3.png

 

 Channel OIperational State Machine:

I4.png

 

Q4: What happens with Internet channel if RIB loses 0.0.0.0/0 prefix over the Tunnel interface?

A4: In this scenario, the channel nexthop will be 0.0.0.0 that means the channel next-hop is lost, but the channel state is still Reachable. At the same time the channel is not available because the channel nexthop is lost.