SWAN Concentrator and WAN Subsystem Troubleshooting Guide

Troubleshooting Tips for the SWAN Concentrator
and the WAN Subsystem
SWAN Concentrator and WAN Subsystem Troubleshooting Guide—426992-008
6-2
Latent Failure Detection (LFD)
Latent Failure Detection (LFD)
The Latent Failure Detection (LFD) feature provides a health check of the configured
SWAN CLIP paths by frequently polling every path. When any path which was flagged
down comes up, an IOPON message is sent to the devices configured on that CLIP.
This message serves as a wakeup call to the LINEs configured, and the lines recover
automatically if they are down due to path failures.
LFD has these considerations:
•
LFD is implemented in the WANBoot process. The corresponding WANBoot
process needs to be up for LFD to work.
•
The SERVER state of the corresponding CLIP needs to be in the STARTED state.
•
WANBoot polls each path every 30 seconds.
•
If a poll on a particular path has failed more than 3 times successively the PATH is
marked as down.
•
If a path has been marked down, the LFD polling is done once every 2 minutes.
This is achieved using LFD:
•
If both paths have failed on a started line, the line goes into "Suspended state”.
When one of the paths comes up, LFD detects that in the next poll and sends an
IOPON message to the device. This message brings the line to a STARTED state
automatically and the LINE recovery is complete.
•
An IOPON message is also sent to the device, if a BOOTP request has come from
the CLIP.
•
In G06.07 and later RVUs, the EMS message indicates the time the PATH went
down and came up.
•
In G06.07 and later RVUs, the health status of a path can be checked by using the
STATUS SERVER command with the DETAIL option. This command displays the
current status, the last time the status changed, and the last BOOTP time of both
the paths.