Upgrading C9200 Stack Question

[RICHARD MESSINGER]

One of my customers has a Catalyst 3850 stack that we are looking to replace with a C9200 stack.

Question is that if we need to upgrade the ios on the switches, can we upgrade member by member and still pass traffic on the members that are not being upgraded.  Today to upgrade the 3850, it will take the entire stack down during the upgrade until all member are at the new software version.  this is a problem in that this is handling his SAN and compute servers and would take the enterprise down.

Hoping the the C9200 will be a good replacement.

[RICHARD MESSINGER · Accepted solution]

Found the answer in a previous thread.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9200/software/release/16-11/release_notes/ol-16-11-9200.html#task_eld_g4n_4gb

Not a hitless upgrade

[balaji.bandi]

When you replacing Cat 3850 with Cat 9200, install latest IOS  XE and put them in to network.

can we upgrade member by member and still pass traffic on the members that are not being upgraded

You can upgrade each switch, you need upgrade all stack members and reboot to get effected.

there is 17.6.X onwards there is fast upgrade to minimise downtime like 15seconds ( never working in my testing).

High level for your question, you need to reboot all stack member after upgrade to take effective.

[Leo Laohoo]

@balaji.bandi, there is a feature called "fast reload" and Cisco has been encouraging people to test it.   We did and the stack master crashed.  

@RICHARD MESSINGER, short answer, no.  Long answer, no.  

Reboot the stack.  This is IOS-XE (and not classic IOS).  There are many bugs related to IOS-XE where the workaround is to cold reboot (pull the power cable) the switch member or the entire stack (which very rarely is the case with classic IOS).

There is another feature Cisco is pushing everyone to beta-test:  ISSU or FSU/eFSU/xFSU.  Every time we try ISSU or FSU/eFSU/xFSU it always results in a TAC Case.  Like I say in other responses, ISSU or FSU/eFSU/xFSU only works in "corner cases" or in a lab.  When it will fail, it will do so in a spectacular fashion and may require (I have seen one person in this forum do it) someone to manually yank the power cable out.