New MX 19.1.9 stable release candidate: fixes MX75 becoming unresponsive issue and many more!

[cmr]

Security appliance firmware versions MX 19.1.9 changelog

Important notice

• As of MX 19.1, Cisco Meraki will no longer support USB-based Cellular Failover on the MX and Z platforms.

Legacy products notice

• When configured for this version, Z1 devices will run MX 14.56.
• When configured for this version, MX64(W), MX65(W), MX84, MX100, and vMX100 devices will run MX 18.107.13.

Executive summary

• This is the latest generally available maintenance release for the MX 19.1 release. It contains a key fix for MX75 interfaces becoming unresponsive. There are also fixes for passthrough mode, AutoVPN, and various issues encountered on MX75, MX85, MX95, MX105, MX250, and MX450 appliances. Please read through the full details below.
• We strongly recommend any customers that have experienced issues with unexpected device reboots on MX75 appliances that have not already upgraded to 19.1.8 or higher to evaluate the release. We have seen meaningful improvement for the overwhelming majority of impacted customers that have already upgraded to 19.1.8 and above.
• MX 19.1 has crossed several key adoption thresholds having already been deployed on more than 20% of eligible devices. Based on this and its performance in the field, we are anticipating promoting MX 19.1 to Stable in the coming weeks. We would strongly encourage all customers to start evaluating MX 19.1.

Bug fixes - general fixes

• Corrected an MX 19.1.7.1 regression that caused MX AutoVPN hubs to incorrectly advertise IPv6 IP addresses over AutoVPN. This could cause instability in AutoVPN routing and disruptions to clients that relied on the IPv6 connectivity.
• Fixed a rare issue that could result in packet loss and unstable AutoVPN connections when complex NAT schemes were used between peers. This typically occurred when Carrier Grade NAT was used by the Internet Service Provider.
• Resolved an issue where MX appliances operating in passthrough mode would incorrectly advertise local IPv6 subnets to EBGP peers. The behavior is now consistent between IPv4 and IPv6 subnets after this change.
• Fixed an issue that resulted in MX appliances configured in passthrough mode incorrectly routing ICMP fragmentation needed messages that were generated by the MX itself.
• Fixed an issue that caused MX appliances to incorrectly assess whether the WAN connection was working when the MX’s connectivity checks were redirected to a splash page. Appliances will now treat an HTTP 302 response as a failure, rather than a success when performing WAN health checks.
• Corrected an issue that caused No-NAT uplink overrides to not apply if the L2 PCP field was set to a value other than 0.
• Resolved an issue that could result in an unexpected device reboot when content filtering was enabled and MX appliances lost connectivity to the TALOS URL service. This was also resolved in MX 19.1.8.1.

Bug fixes - limited platform fixes

• Resolved an issue that could cause the IDPS process to fail when making certain configuration changes to WAN interfaces (such as disabling or enabling an interface). This issue may have also contributed to high device utilization. This resolves known issue MX-34504.
• Fixed a rare issue that could cause the WAN and LAN ports on MX75 appliances to become unresponsive until a device reboot was performed.
• Corrected an issue that resulted in MX75, MX85, MX95, MX105, MX250, and MX450 appliances reporting erroneously higher device utilization on the Meraki Dashboard.
• Corrected an issue that could result in duplicate Client VPN and AutoVPN Event Log entries on MX75, MX85, MX95, MX105, MX250, and MX450 appliances.
• Resolved a very rare issue that could result in firmware upgrades from MX 18.1 failing to complete successfully on MX75, MX85, MX95, MX105, MX250, and MX450 appliances.
• Corrected an issue that resulted in MX75, MX85, MX95, MX105, MX250, and MX450 appliances failing to forward GRE traffic.
• Resolved an issue that resulted in HTTP traffic being routed improperly when HTTP Content Caching was enabled.

Known issues status

• This list is being reviewed and updated.

Known issues

• During the upgrade process, MX appliances upgrading from version prior to MX 19 may experience a failure to properly classify traffic. This issue will be resolved once the appliance has completed the upgrade to MX 19. (MX-36307)
• Due to an issue under investigation, MX appliances may incorrectly route traffic destined to subnets learned through eBGP over a Non-Meraki VPN connection. (MX-34803)
• When failover is configured between non-Meraki VPN tunnels, the Route Table page on Dashboard may incorrectly show the route for the primary VPN tunnel is inactive. (MX-36316)
• During the upgrade process, MX appliances upgrading from versions prior to MX 19 will experience a failure to connect to non-Meraki VPN peers if any VPN peer names contain a space. This issue will be resolved once the appliance has completed the upgrade to MX 19. (MX-36312)

[cmr]

I like this in the notes:

• MX 19.1 has crossed several key adoption thresholds having already been deployed on more than 20% of eligible devices. Based on this and its performance in the field, we are anticipating promoting MX 19.1 to Stable in the coming weeks. We would strongly encourage all customers to start evaluating MX 19.1.

[ww]

I like the fix for MX-34504 even more 

[cmr]

There is another around device utilisation as well, I have scheduled the upgrade on my MX75 and we will see!

[RaphaelL]

I will be curious to see that ! Keep us updated !

[cmr]

Applied and on the reboot it just stayed orange...  Pulled the power and it rebooted okay.  One to not trigger remotely for the moment!

[cmr]

Also noticed this about 10 minutes after the upgrade:

Intrusion detection rules update: snort_rules_version: 20250612-1532

Interesting that it needs to apply a version from almost a month ago...

[RaphaelL]

Only took like 6-7 months but we got it !

I will be rolling this update on 1500 networks if it passes our regression tests

[RaphaelL]

Welp ... I still have the same issue, whenever I enable / disable a unused WAN interface on a MX68CW the MX crashes.

[RaphaelL]

So it's not a crash it's "just" a loss of connectivity up to 2mins. But Meraki calls this a feature 

God I love MXs !

[RWelch]

Interesting.....same time period over separate days (no config changes other than a different MX firmware).  Anyone else have similar results (1/2 of the avg device utilization)?

MS 19.1.8.1 (above)

MX75 avg device utilization 21%
MX68W avg device utilization 17%
MX105 avg device utilization 12% 

MS 19.1.9 (above)

MX75 avg device utilization 10%
MX68W avg device utilization 7%
MX105 avg device utilization 6% 

[jimmyt234]

Your experience lines up with this bug fix: 

• Corrected an issue that resulted in MX75, MX85, MX95, MX105, MX250, and MX450 appliances reporting erroneously higher device utilization on the Meraki Dashboard.

[cmr]

I think this tells a story:

That is for an MX75.   Interesting that the MX68W for @RWelch also shows a drop...

[RaphaelL · Accepted solution]

This is a MX68 that is overutilized / undersized ( 150++ clients ) : 

Nice improvement

[Dunky]

Whereabouts are you seeing this graph @RaphaelL ?

I see 19.1.9 is now classified as a stable release so I have just upgraded my test MX85 to it ok.

[Dunky]

Just realised its in the Security Centre.  Would be useful on the actual appliance page.

[RaphaelL]

Organization -> Summary Report -> Select your network and scroll down to the bottom of the page.

https://documentation.meraki.com/MX/Monitoring_and_Reporting/Device_Utilization

[Dunky]

haha yeah, I found it just before you replied 🙂  Thanks.

[jimmyt234]

This slipped under my radar but 19.1.9 is now considered stable?! A new stable appliance firmware is now  available on Thu, 31 Jul 2025 - The Meraki Community

Which can be seen from the schedule firmware upgrade menu:

But nowhere to be seen under Organization>Firmware:

[cmr]

It is in Other available versions for some reason, may be as 18 is also still stable...