The router went down or unreachable or inaccessible, and there were no log messages indicating the cause.
The list of actions one can take to identify the reason why the router is down, unreachable, or inaccessible is provided below.
1. Every client has their own servers, which are constantly querying the files in /var/logs/messages, syslog, chassisd, and other folders. Please ask customer to upload all the last fetched logs from all the files and upload them to the case. This can be useful in determining whether a hardware issue, etc., caused the router to become unavailable or go down.
2. Inquire whether any activities or power maintenance windows occurred at the site.
3. Examine the PEM and RE leds. Here, there are three scenarios that could present issues.
a. If there is no LED on RE, you can ask customer to power cycle the router and see if you see LED for RE.b. In certain router models, the RE is installed within the CB. It is necessary to check the health of the CB, as it supplies power to the RE. To see whether it helps, consider swapping the CB with the same RE. Swapping between RE and CB will help you in narrow on the issue. You may need to raise a proactive RMA here for additional part for swapping. So you need to create RMA for RE or CB depending on the outcome.c. Occasionally, you may notice that the PEM has an amber led or no LED at all, which is the real issue. This lets you know that the router was eventually brought down by a failed power supply. So you need to create RMA for PEM.
4. If none of the above steps are effective, then check the console. This is very important.
a. Connect to the console and observe the output on the router. Sometimes, it displays hardware or disk failure logs for the RE, which can help identify the problem.b. If nothing appears on the console, try reconnecting and performing a power cycle on the router to see if it starts displaying logs. You can also try changing the console cables to see if that helps.