If an MX router's Routing Engines (REs) are connected to a terminal server and the server configuration is incorrect, both REs can end up being stuck while trying to load Junos OS due to characters being sent into the terminal server.

This article explains why this happens and how to resolve the issue.

Both REs may be stuck trying to load Junos OS. Checking the console port shows the following persistent message: 

WARNING: History shows a reset caused by ,J02

Sometimes, the REs may boot up after several minutes, but if a reload is performed, the REs get stuck again.

Incorrect configuration in the terminal server ( flow control enable ) is seen to result in characters being sent via the console that block the booting of Junos OS.

This can also happen due to noise in the console cable.

To boot up the router correctly, remove the console cable from the REs. Perform the following steps:

1. Disconnect both console ports from the REs.

2. Reboot both REs.

3. Check the configuration in the terminal server to use the recommended setting for a router.

   Refer to Connecting the MX480 Router to a Management Console or Auxiliary Device for more information.