Hi jft-san,
I tested on 15.1X53-D56.
Whichever of the following commands I use, Both consoles can be used at the same time, and a startup message is displayed only on RJ45.
set system ports auxiliary port-type mini-usb
set system ports auxiliary port-type rj45
I think that the rj45 command is an unexpected operation.
Regarding the behavior that boot message still appear on rj45 port, For JTAC to say, It is under investigation and PR was created.
This PR is not still published.
<Supplementary information>
The following PR is old information.
[PR1163604 - Mini-USB support not avialable on EX2300 and EX3400]
https://prsearch.juniper.net/InfoCenter/index?page=prcontent&id=PR1163604
JTAC answer is...
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This PR has been fixed in 15.1X53-D50 and later releases.
It means we are supporting mini-USB on EX2300 and EX3400 since 15.1X53-D50.
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Regards,
GENC