We made the jump from the EX4300 to the EX4400 this year and while things have been good, we’ve seen a number of bugs and issues with the early software releases.
If you run into issues with Virtual Chassis, my first suggestion is to check the software release.
By default, the QSFP28 ports on the back of the Juniper EX4400 should be setup as “Virtual Chassis” ports for stacking. You can issue the following command to change the configuration if needed;
request virtual-chassis mode network-port disable reboot
The issue I found is that ~ 70% of the time a Juniper EX4400 would fail to see the Virtual Chassis ports (and fail to “stack” properly) if it was running 21.2R3.8 software – the software release Juniper was shipping on switches sold in early 2023. An upgrade to 21.4R3-S3.4 or even the current recommendation of 22.2R3-S2.8 immediately resolves the issue.
I’ve also observed a number of odd PoE/interface issues impacting Juniper MIST Access Points, Kronos clocks along with other assorted PoE devices, such that they receive power but are unable to establish a LINK on the port with either 1Gbps or 2.5Gbps.
I’m currently running 21.4R3-S3.4 in production but we’re seeing a lot of intermittent BFD timeouts which we suspect is a software issue. We’re currently testing 22.2R3-S2.8 in a number of locations.