Junos OS

Hello Colleagues, 

We are planning to upgrade 5100 QFX VCF of 10 switches (2 spines and 8 leaves), to minimize the downtime we will divide it to ODD VCF (S1,L1,L3,L5,L7) and Even VCF (S2,L2,L4,L6,L8) , re-route traffic via one and upgrade the other and vice versa, I know we sill have 10sec down time during the re-route but it is best we can get. 

My question, 

I know that switches in the same VCF should have the same Junos version in order to work properly, but I noticed in some tests that line cards even though when they are using different versions they are still seen in the VCF so the question are the line cards in VCF with different Junos version are still able to forward the traffic as L2 device?

Asking for such strange possibility as it seems we have a lot of possible single point of failures (servers that connected with 2 connections to Odd leaves only or Even leaves only), and since we will upgrade the half VCF with odd numbers all together then the half VCF with even numbers all together, those few servers will suffer, so if these leaves continue to forward traffic even with different Junos version then we can upgrade one leave  a time and avoid some downtime for these unlucky servers.  

Hello Alex,

When the linecard runs a different version from the master, it should transition to inactive state and stop passing traffic.  It is not expected to see it passing traffic, but if it does, you cannot trust it is stable, it will stop passing traffic any time.

Hope this helps,

Randall,

Thanks for the answer, actually I thought the same.

but I got an answer from Juniper SME who supports us and he mentioned, that they should still forward traffic even if they are on different code versions in the same VCF during that upgrade cycle.and This should allow usto upgrade one at a time for switches that have single connect servers.

Not sure I can test that in advance so wanted to be sure of this point, but without making sure 100% it works we will not proceed with that.

Hi Alex_SK,

If you are planning to upgrade the VCF using NSSU, then the answer is yes. The linecards running a different OS, should still forward traffic. If you were planning to do one half and then the other one with the regular upgrade method then one half of the VCF will become inactive.

You can check these links to know more about NSSU. The upgrade will take like 10-15mins for each switch.

https://www.juniper.net/documentation/en_US/junos/topics/concept/nssu-vcf.html

https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/nssu-ex-series-cli.html

If you are upgrading from a 14.1 code to a newer one NSSU won't work.

https://prsearch.juniper.net/InfoCenter/index?page=prcontent&id=PR1087893

https://www.juniper.net/documentation/en_US/release-independent/junos/topics/reference/general/nssu-qfx5100vcf.pdf

If this solves your problem, please mark this post as "Accepted Solution". 

-Gustavo