Meraki MX and ATT Arris GBW210 - Failover Issues

[jindivik]

We have a Meraki MX setup behind our ATT Arris which is set to IP passthrough. We also have a backup circuit setup and when we test failing over the ATT modem provides the MX with a Internet Down alert page that essentially makes the MX believe its still connected to the internet causing it to never fail over.

Is there a way to disable this feature or should we be setting the ATT modem up in a different manner?

[jdsilva]

It should still fail over, but it'll take up to 300 seconds to happen. Are you waiting the 5 minutes?

https://documentation.meraki.com/MX/Firewall_and_Traffic_Shaping/Connection_Monitoring_for_WAN_Failo...

[jindivik]

Yes while on the network locally you get a splash page produced by the Arris that says the internet is down which we assume is why the MX doesn't recognize that its offline because the ARP/DNS queries still route somewhere.

[jdsilva]

The connection to the cloud will be broken though, which is why I'm assuming that it should still failover. You very well could be right though and that splash page is enough to trick the MX.  How long have you left it in a failed state for?

[jindivik]

About 10 minutes but honestly anything longer than the already long 5 minutes is to much. ATT has stated that there isn't a way to disable this feature so probably looking at trading their modem in for something else if possible. Hoping someone here has dealt with this before though.

[jdsilva]

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@jindivik wrote:

Hoping someone here has dealt with this before though.

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I wish I had more to offer you here, and honestly I'm a bit surprised that simply putting up a captive portal page is enough to fool the MX into thinking there's Internet available on that port. In my mind this should be logged as a bug and fixed. 

[pkinnison]

Also it is my understanding that the MX does a number of checks before it fails a WAN Interface and goes to cellular.    This for sure can take some time  up to 5 minutes or so.    One key factor is the ability to communicate with a designated IP for example Google's DNS  8.8.8.8,  but also the Meraki Cloud etc.

I don't know all of the specific checks that the MX Performs before it fails over but I would like to hear from a Meraki Engineer what they are.

Thanks

PK

[Wazz]

Is it a carrier provided router?

Do you have to use the ATT router? As in it cannot be replaced with a more fit-for-purpose router? I

[jindivik · Accepted solution]

Identified the issue for anyone else in the future. There is an option under Diagnostics -> Event Notiications and disable the Broadband Status Notification.

Doing an nslookup before and after this showed that the router resolves all DNS entries if the router is down to the 192.168.1.254 and disabling this notification resolves the problem.

[Wazz]

Awesome mate! I was going to recommend throwing the ATT router in the bin and putting a proper router in! 😛