Discovered a hidden "feature" in MS125-48LP to start hunting all VLANs if Internet is lost

[Boyan1]

Hi everyone,

I recently discovered the hard way a hidden "feature" in MS125-48LP to start hunting all available VLANs if Internet is lost EVEN IF the switch is setup with static IP. That's what blows my mind, manually configured switch, losses Internet connectivity, starts hunting all VLANs and obtains DHCP IP in the first VLAN that would offer DHCP even if that VLAN is completely isolated from the Internet so the hunt mechanism is a fail right away but my question is upstream from this - why? Why start hunting if the switch is configured with static IP?

The kicker is that even after Internet connectivity is restored, the switch does NOT revert back to its original statically configured VLAN and IP - the only way to do this is to power cycle it. This means that a random brief loss of visibility to Meraki's cloud throws the device into infinite lockout status where recovery is only possible by manual power cycle. 

Is there any way to disable this marvelous feature?

Thanks

~B

[Ryan_Miles]

This is how Meraki switches have always worked. Internet issues aside if you configure a static IP that is not valid the switch will revert to DHCP in order to try to get an IP and connect to dashboard. Being that Meraki devices are cloud managed there are multiple failsafe routines to ensure it can find a way to dashboard.

Also, if you give it some time the device should revert to using it's static if that's a valid config. It shouldn't need a reboot.

[Boyan1]

@Ryan_Miles Thank you for the quick reply Ryan, is the logic publicly known (and available to share with us) which drives the criteria of "if you configure a static IP that is not valid" ?

What is the logic to test yes/no whether said static IP is not valid, and then trigger the hunt?

And of course my question has part (b) - can that be disabled?

Thanks

Boyan

[PhilipDAth]

@Ryan_Miles did provide a link to the documentation on this.

https://documentation.meraki.com/General_Administration/Cross-Platform_Content/Behavior_during_Conne...

It doesn't stop at one VLAN - it will keep trying every VLAN it can till it can re-establish connectivity with the Meraki cloud.  Your static configuration is not lost - the switch will still retain it.

Meraki is completely cloud managed, and it is great survivability features like this that allow you to recover from faults (often caused by human accident) without having to visit a site.

[PhilipDAth · Accepted solution]

No, it can not be disabled.

[cmr]

We leave most of our switch management IP addresses on DHCP, but do select a VLAN and as long as that is connecting to the internet then it does use that VLAN.  Do you have a particular reason to use static IPs for switch management?

[BlakeRichardson]

How can this feature be annoying, it means your hardware is trying to use a stop gap measure to retain connection to the dashboard which in turn allows admins to run tests from the switch while troubleshooting.