[j-nsp] Rock-solid JUNOS for QFX5100

[Ross Halliday]

Dear List,

I'm curious if anybody can recommend a JUNOS release for QFX5100 that is seriously stable. Right now we're on the previously-recommended version 17.3R3-S1.5. Everything's been fine in testing, and suddenly out of the blue there will be weird issues when I make a change. I suspect maybe they are related to VSTP or LAG, or both.

1. Add a VLAN to a trunk port, all the access ports on that VLAN completely stopped moving packets. Disable/delete disable all of the broken interfaces restored function. This happened during the day. I opened a JTAC ticket and they'd never heard of an issue like this, of course we couldn't reproduce it. I no longer recall with confidence, but I think the trunk port may have been a one-member LAG (replacement of a downstream switch).

2. New trunk port (a two-port LACP LAG) not sending VSTP BPDUs for some VLANs. I'm not sure if it was coincidence or always broken as I had recently began feeding new VSTP BPDUs (thus the root bridge changed) before I even looked at this. Other trunk ports did not exhibit the same issue. Completely deleted the LAG and rolled back to fix. This was on a fresh turnup and luckily wasn't in a topology that could form a loop.

Features I'm using include:

- BGP
- OSPF
- PIM
- VSTP
- LACP
- VRRP
- IGMPv2 and v3
- Routing-instance
- CoS for multicast
- CoS for unicast
- CoS classification by ingress filter
- IPv4-only
- ~7k routes in FIB (total of all tables)
- ~1k multicast groups


There are no automation features, no MPLS, no MC-LAG, no EVPN, VXLAN, etc. These switches are L3 boxes that hand off IP to an MX core. Management is in the default instance/table, everything else is in a routing instance.

These boxes have us scared to touch them outside of a window as seemingly basic changes risk blowing the whole thing up. Is this a case where an ancient version might be a better choice or is this release a lemon? I recall that JTAC used to recommend two releases, one being for if you didn't require "new features". I find myself stuck between the adages of "If it ain't broke, don't fix it" and "Software doesn't age like wine". Given how poorly multicast seems to be understood by JTAC I'm very hesitant to upgrade to significantly newer releases.

If anybody can give advice or suggestions I would appreciate it immensely!

Thanks
Ross