3850 upgrade to 16.6.5 - odd SVI behaviour post-boot

[james.brunner]

Hi all,

We have a test Cisco 3850 stack running 16.3.6 IP Base and thought we'd try 16.6.5 (other stacks in our estate are running 16.6.4a without issue on all LAN base, IP base and IP Services).

The upgrade went fine - the console output was fine. Except once the stack rebooted no IP traffic would pass - a "sh arp" showed the local SVIs for each VLAN but all other ARP requests were reported as "Incomplete". The configuration was exactly the same after the upgrade apart from a few added commands but nothing that I could see as affecting the IP layer.

As a long shot I shut/no shut the SVI interfaces for each VLAN and service resumed as normal - ARP reported as expected, OSPF kicked into life etc. To make sure I wasn't going slightly insane, I saved the configuration and bounced the stack but once rebooted the same issue returned. A bounce of the SVIs interfaces cured it.

Has anyone else tested 16.6.5 and come across this - or am I missing something really obvious?

Thanks! JB.

[james.brunner · Accepted solution]

Quick update.

We tried this on another single standalone switch and got the same results. However, a test on yet another single stack switch worked fine (with SVIs) and another single stack switch worked (without SVIs). I can't see any reason for the differences but for now we've taken the decision that, even being a star version, 16.6.5 is not for us - we'll stick with 16.6.4a for now.

I feel bad because if we had more time we'd open a TAC case to work through this but who has time to spare these days when there's a simple solution?

JB.