VII. Router Diagnostics

Troubleshooting an unexpected router reboot

Products:
Vigor 2620Ln
Vigor 2760
Vigor 2762
Vigor 2765
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Keywords:
crash
debug
debug log
diagnostics
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In normal operation a DrayTek router will keep running indefinitely. You can check the Vigor router's current uptime by going to the Online Status page.
This can typically be found in the router's web interface in [Online Status] > [Physical Connection]

The System Uptime field indicates how many hours : minutes : seconds the unit has been running for from the last power cyle or router reboot. The System Uptime is separate from the WAN Up Time, it's possible for the WAN to disconnect / reconnect without the router's system uptime being affected.

Possible Causes of reboots

If the System Uptime is lower than expected this can indicate that the router has been rebooted recently. There are multiple reasons that could trigger a reboot (Power Cycle, Firmware Update, applying setting changes) and this article goes into details on how to determine the most likely reason and if it's an unexpected reboot, how to go about troubleshooting the cause.

 Some possible reasons for a router reboot are:

Planned or manual reboot

  • Power Cycle via physical on / off switch
  • Reboot via Web UI "Reboot System"
  • Reboot via Web UI to apply setting change
  • Reboot via Web UI Firmware Upgrade
  • Reboot into TFTP mode via Web UI
  • Reboot via CLI command
  • Reboot via pressing physical reset button
  • Reboot via Firmware Upgrade Utility
  • Reboot via Web UI Schedule
  • Reboot via VigorACS (Manual or Schedule)

Unplanned reboot

  • Reboot upon detection of a change in DSL mode (from ADSL to VDSL or vice versa).
  • Faulty Power Supply (Either cutting out or providing low voltage or amperage)
  • Power Cut or Brownout (if the router's power supply isn't using a UPS)
  • Reboot via Watchdog

Diagnosing Causes of reboots

In the event that the router's uptime is lower than expected and the cause of the reboot isn't apparent, the following steps are the recommended methods to diagnose the cause of the reboot.

Following these steps may resolve the cause of the reboot in some cases, and if not, will help the DrayTek technical support team significantly in assisting you. Determining the root cause of the reboot will allow the support team to resolve your router reboot issue more quckly:

1 - Check Firmware

Ensure you have the currently released firmware installed on your router.

Current versions of firmware for each router are listed here, with downloads of current and previous firmware versions available:
DrayTek UK Downloads

Select your model of router, and download it to your local drive.

The simplest way to upgrade the firmware is via the Web GUI. Follow this guide:
How to Upgrade Firmware via the Router's Web Interface

Make sure to take a Configuration Backup before upgrade the firmware as a precaution.

2 - View Router Logs

There maybe useful information regarding the reboot issue in a syslog. To capture this log information from the router, follow this guide:
DrayTek Syslog Setup & Usage Guide

If a restart occurs, the timestamp on the Syslog messages sent by the router will briefly reset to "00:00:00" (hours:minutes:seconds) before reconnecting to the Internet to get the correct time.

Note: If the router is restarting unexpectedly, the router's USB syslog facility cannot capture events leading up to and immediately after the restart, because of the delay in writing syslog files to USB storage.
It is recommended to use a PC with the DrayTek Syslog software or another device (NAS, Raspberry Pi) with a generic Syslog utility on site to receive syslog messages from the router.

If you need to contact technical support, you may be asked for the syslog.

3 - View Router's Debug Log

When a reboot occurs, access the router's Command Line Interface as soon as possible and record the router's debug log output, which the support team can utilise to troubleshoot the cause of the unexpected reboot.

To access the router's Web Console, access the router's Web Interface and click the "sliders" icon in the top right menu of the router's web interface:Alternatively, access the router's Command Line Interface from:
Windows
Apple Mac OS X

In the router's Command Line Interface, type in this command and press enter:

sys ver dbg

Please save the text of this output. If you need to contact DrayTek technical support you may be asked to send this output to them. The output is useful for the engineers and gives debug information on which operation was being performed at the time of the reboot and in some cases can then be traced back to a specific function.

The process that records this error log is called the "Watchdog" which is listed above as one of the possible causes of a router restart. The Watchdog is a process that runs alongside the router's main DrayOS operating system, which periodically checks whether the router is still functioning normally. If this check fails, the Watchdog forces the router to restart and records the router's last operation into the debug log.

The router's debug log is handled differently on older and newer router models:

DrayTek Vigor routers before Vigor 2860

i.e. Vigor 2830, Vigor 2850
"sys ver dbg" log data is stored in the router's RAM memory and is cleared if the router loses power or is power cycled
DrayTek Vigor 2860
and later

i.e. Vigor 2952, Vigor 2762
"sys ver dbg" log data is stored in the router's flash storage, it is stored there until cleared with the "sys ver dbg reset" command.
The log data is stored after power cycle, factory reset and firmware reflash.

You may see an output similar to this...

Reboot logged by Router:

Note: In the example above, the router's currently running firmware (3.8.9.1_BT) is newer than the firmware in the debug logs's CURRENT_VERSION (3.8.7_RC4). This indicates that the debug message logged did not occur when running the current firmware and is from an older event.

The debug log information can be cleared with the "sys ver dbg reset" command. If the router restarts unexpectedly, it will create a new debug log, overwriting the previous entry.

No reboot logged by Router:

This is displayed when no debug log has been recorded by the router. On older models, this could mean that the router was power cycled.

To clear the debug log message manually on newer models, use the "sys ver dbg reset" command.

4 - Test without USB Modems & Devices

If you have any USB dongles or other devices such as storage, printers, connected to any of the USB ports, unplug these. Then monitor to see if there is any improvement.

If the router becomes stable with the USB devices disconnected, there are two possible causes of this:

  1. Power issues - A USB modem that draws more power than the router can supply could affect the stability of the router's power supply (see Step 8). This can be worked around by connecting the USB modem to the router through a powered USB hub.
  2. Router firmware - Caused by an interoperability issue between the router and the peripheral device. This should be logged by the router after it occurs, in the router's debug log (Step 3).

5 - Simplify Configuration / Disable Features

To check if a particular function is causing the reboot, take a configuration backup of the router:
How to Back up the Router Configuration

Then disable specific features / functions to observe whether this stops the router from restarting. Checking the router's Syslog output can be useful for finding clues of which services to investigate if there are syslog messages relating to that feature around the time of the restart.

For Example - disable the router's Wireless, and then monitor the router for a period of time and if that hasn't resolved it, try re-enabling that facility and disable another, such as Bandwidth Limit. If this allows a specific feature to be identified then contact the DrayTek technical support team with further details so that it can be investigated.

When you're done testing with services disabled, reload the configuration backup to restore the router to its original state.

6 - Check for Scheduled Reboots

Check if you or someone else has set a reboot schedule. This will be logged by the router's Syslog output, and these settings are configured in two locations on the router:

Web Interface

[System Maintenance] -> [Reboot System]

Scheduled Reboot Settings

Schedules a reboot to occur at the time specified by the schedule entry linked i.e. 1 links to schedule entry 1 in the [Applications] > [Schedule] menu

Command Line Interface

View status: "sys autoreboot ?"

Disable: "sys autoreboot off"

Schedules a reboot to occur at the specified interval, which starts counting when the router is power cycled or when the command is initially entered.

7 - Check VigorACS

If the router is managed by VigorACS, check whether the reboot / repeated reboots are initiated or scheduled from the VigorACS server that the router is managed by.

In VigorACS 2, scheduled reboots are configured from [SYSTEM MENU] > [Maintenance] > [Device Reboot]

8 - Check Power Supply

Make sure the PSU used for the router is the one supplied with the product, using an alternative PSU can damage the unit or provide inadequate power for that router model's functionality, which can potentially affect router stability.

Check that the power supply being used with the router supplies the correct voltage and amperage to match the Vigor router's listed Power Consumption shown on the label on the underside of the router.

For instance a Vigor 2862ac shows:
Power Consumption:27W(MAX.)
Power Input: 12V === 2.3A

This means it requires a power supply with at least that specification - using a power supply with a lower power output could result in unexpected behaviour or reboots, when using the full capabilities of the router.


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