Issue with MX19.2.4 (Release candide)

[John_R_Gudmann]

Hi

We just made a upgrade to the release candida MX19.2.4.

we have seen issue with older hardware like Z3C-WW; MX64; MX64W and MX65.

When there is Internet using WAN the connection goes down as soon as there a bit of load on the VPN tunnel (up and down ever  0.30-1 hour). when a device is using simcard (4G) no problem is seen.

We have same firmware running on many other MX67; MX68 MX95 so a bit concerned this time since Meraki was pushing for update on this model end of Jan 2026 since they where running critical version

Downgrade to stable version 19.1.11 seems to solve this.

Has any other seen this? Is this a known bug? 

Thanks John

[alemabrahao]

Legacy products notice

• When configured for this version, MX64(W), MX65(W), MX84, MX100, and vMX100 devices will run MX 18.107.13.

[John_R_Gudmann]

I know they have listed that in the version.. never the less it showing19.2.4 (not now after I have downgrade) and you can also see the status of the link going up and down

[RaphaelL]

You migrated from what version ? 

It seems like your device is unable to install the firmware and is stuck in a upgrade firmware loop 

[RaphaelL]

I would open a case , not so much we can look / do at this point

[mlefebvre1]

The firmware version you see in dashboard and in API is what the network is set to in the firmware upgrades page, not the actual version running on the device, only Meraki Support can actually see what firmware is running on the device

[jbright]

I have seen the exact opposite of this recently where a Z3 was dropping off the internet about every hour running 19.1.11 firmware. It has two site-to-site VPN connections configured on it. I upgraded it to 19.2.4 over the weekend and it has been rock solid since.

I also noticed that the total bandwidth of the Z3 has now been increased from 100 to 200 megabits since it was upgraded to the new firmware. I have not seen that feature documented anywhere, but it shows up as an option on the Traffic Shaping page and the bandwidth speed test in the dashboard now shows 205 megabits for the download speed.

[PhilipDAth]

That is due to the new software design, which now allows the use of multiple CPU cores for some internal operations.

I'm going to call it 99.9% good.  I've only had to disable multithreading at one client (via support), because it kept causing regular crashes on their MX.

[jbright]

@PhilipDAth I was aware of the multi-threading feature of the MX19.x firmware on the MX appliances, but I did not know that it now works on the Z3 too until I upgraded it to the 19.2.4 firmware. The increased bandwidth only became available in the newest version of the firmware. It was not available in the 19.1.x firmware. And since the 19.2.x firmware is the last major version for the Z3, maybe this was a parting gift from Cisco 😉