The above logs are generated whenJUNOS library on the RE tries enhanced mode (rcmd mode)to connect with the FPC.

Below syslog messages can be seen when the RE tries to connect to the FPC after some events, for eg FPC is restarted and it tries to connect to the RE.

Apr 12 03:31:47.000 2024 xxx_RE0 fpc3 daemon.err rshd[616857]: Second port outside reserved range.

Apr 12 04:31:46.000 2024 xxx_RE0 fpc3 daemon.err rshd[618008]: Second port outside reserved range.

The above logs are generated when junos JUNOS library on the RE tries enhanced mode (rcmd mode)to connect with the FPC. The rshd(rlogin daemon) on the FPC do not understand this protocol and thus the above log is generated. The RE then falls back to normal connection mode and connection is made.

These are harmless logs and can be safely ignored. If you want you can suppress these logs in the syslog configuration using the below KB.

https://supportportal.juniper.net/s/article/Junos-Platform-Example-How-to-prevent-certain-syslog-messages-from-being-written-to-the-log-file