The procedure all depends on what redundancy your connected devices have. If they are mainly hypervisors and other devices that are multihomed, this can be done quite nicely. The more single-attached devices you have, the longer the downtime.
I guess you have already read this guide:
https://www.juniper.net/documentation/us/en/software/nce/nce-171-qfx-vc-upgade/topics/topic-map/nce-171-qfx-vc-upgrade.html
It is easier to handle 2 member VCs in this scenario. Perhaps splitting the 4 member VC into two VCs would be a good idea.
Another idea is to go for eVPN on the QFXes. This may require a license upgrade, but gives you superior flexibility and any (well, most) upgrade issues will become a memory only:
https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/example/evpn-vxlan-qfx5110-l3-vxlan-gateway-non-collapsed.html
Original Message:
Sent: 09-23-2023 05:01
From: Suli
Subject: Junos Upgrade QFX5110 and EX3400 in VC
Hi all,
I need to upgrade my switches soon with minimum outage downtime. I need your advice on this. See below for the VC setup. I would like to upgrade them to a recommended version. So which method should I apply it to do the upgrade. I understand in various discussions in the community that you should not use NSSU, because it can cause many issues during the upgrade procedure and it can cause a longer down and upgrade time with low success rate. Another method is to upload the junos image on master node and have it upgrade the rest of the switches and then reboot all switches member "request system reboot all-members". This will create a full downtime with less time than NSSU, so is probably better scheduling a maintenance window. Possibly the last method is to perform a manually upgrade by breaking the VC to upgrade each switch individually. So first upgrading the linecard nodes and after the backup and master node. So can anyone suggest the best method (best practice) to upgrade the QFX5110 and EX3400 in VC.
VC setup:
4 member of QFX5110 in VC (20.4R3.8 to 22.2R3-S2)
2 member of QFX5110 in VC (20.4R3.8 to 22.2R3-S2)
2 member of EX3400 in VC (20.4R3.8 to 21.4R3-S4)
thanks