Anchoring Redundancy Support for Pseudowire Subscriber Logical Interfaces
Prior to Junos OS Release 17.3, MPLS pseudowire deployments using pseudowire subscriber logical interface did not support a mechanism to handle anchor Packet Forwarding Engine (PFE) failure. This leads to traffic and subscriber session loss when a Flexible PIC Concentrator (FPC) hosting logical tunnel on which pseudowire subscriber logical interface is anchored, goes down. To avoid this session loss, pseudowire termination applications demand redundancy support to move the session to another anchor PFE without losing traffic statistics.
Starting from Junos OS Release 17.3 onwards, anchor point redundancy feature provides anchoring support of pseudowire subscriber logical interface on redundant logical tunnel (rlt) interface in active-backup mode. The rlt interface hosts multiple logical tunnels. As logical tunnel is a loopback device, the failure of PFE also indicates failure of the logical tunnel hosted on that PFE. This property is used to detect failures faster.
To provide anchor point redundancy, enhanced aggregated infrastructure in PFE is used. Enhanced aggregated infrastructure requires minimum one control logical interface (IFL) which needs to be created on rlt interface. Both transport and services IFLs created on pseudowire subscriber logical interface will be stacked on rlt control IFL. This IFL stacking model is used for both redundant and non-redundant pseudowire subscriber logical interfaces.
 | Note: Redundant logical tunnel interface allows 32 member logical tunnel IFDs. However, pseudowire subscriber logical interface hosted on rlt interface limits logical tunnel IFDs to two. |
The following events can cause a logical tunnel IFD to fail and have to trigger its removal from a redundant group:
- Hardware failure on Modular PIC Concentrator (MPC) or Modular Interfaces Card (MIC).
- MPC failure due to microkernel crash.
- Administratively taking MPC or MIC offline.
- Power failure on MPC or MIC.
