MX68CW warm spare configuration and cellular

[superfly]

The setup is as follows.

2 x MX68CW's both with cellular and both with INTERNET 1 port hooked up

.

What I'm finding is that if the master INTERNET link fails, the cellular will kick in and continue the master being the master but now using cellular instead.

Is there a way to prefer the warm spare MX over using cellular on the primary MX?

[Adoos]

Are both MX devices connected to the same device upstream on Internet1? 

[superfly]

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@Adoos wrote:

Are both MX devices connected to the same device upstream on Internet1? 

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Yes they are both connected to an internal switch (i.e. not directly to an ISP)

[jdsilva]

That is incorrect behavior according to Meraki documentation.

https://documentation.meraki.com/MX/Deployment_Guides/MX_Warm_Spare_-_High_Availability_Pair#Cellula...

If your MX is failing to cell instead of to the standby when WAN1 goes down then that would be a bug. Call support and get the involved.

[PhilipDAth]

In addition to @jdsilva 's link, note this important bit:

Cellular Failover Behavior 

Meraki does not currently support any cellular failover with a high availability (HA) pair; as we do not perform connection monitoring on cellular uplinks (as of MX 10.X+), which is necessary for HA uplink failover.

[superfly]

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@PhilipDAth wrote:

In addition to @jdsilva 's link, note this important bit:

Cellular Failover Behavior 

Meraki does not currently support any cellular failover with a high availability (HA) pair; as we do not perform connection monitoring on cellular uplinks (as of MX 10.X+), which is necessary for HA uplink failover.

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So is the image posted by @NolanHerring what actually happens but is not supported?

[NolanHerring]

Is the 'Internet 1' connection plugged into both ports on port 1 on each MX the 'same' Internet?

Meaning if it goes down, both MX lose the connection?

If so then it makes sense that the Primary Cellular kicks in

Otherwise, if both Internet circuits are actually different, and don't both go down at the same time, then indeed the warm-spare WAN 1 should take over.

[NolanHerring · Accepted solution]

This image here best explains it:

[superfly]

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@NolanHerring wrote:

This image here best explains it:

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Yeah I saw that diagram which is why I asked the question.

[superfly]

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@NolanHerring wrote:
Is the 'Internet 1' connection plugged into both ports on port 1 on each MX the 'same' Internet?

Meaning if it goes down, both MX lose the connection?

If so then it makes sense that the Primary Cellular kicks in

Otherwise, if both Internet circuits are actually different, and don't both go down at the same time, then indeed the warm-spare WAN 1 should take over.

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Yeah that's pretty obvious 🙂

I'm manually disconnecting the cable from the master MX so the upstream is not the issue here.

[superfly]

Some further information that I've just worked out.

The 2 MX's are directly connected for HA. Their INTERNET 1 port is connected to an internal network switch. I have no downstream switch currently so I'm directly plugging into another port on the MX with my laptop.

So with it all hooked up, 1 MX shows as the Master, the other is the PASSIVE. I then disconnected INTERNET 1 from the master. It causes the PASSIVE mx to become the master and on the primary MX it activates the Cellular. As you can see here.

What I'm finding is that no matter which MX I plug my laptop in, it works as expected. This is even the case when both INTERNET 1 connections are up. I think I'll have to hook in a downstream switch and then test to see where the traffic is going. Even though the Cellular comes up on the primary MX, downstream traffic may go via the newly promoted primary MX.

I'll report back.

[jdsilva]

That makes sense. Without anything on the LAN side VRRP can't do its thing properly for the LAN clients. 

[NolanHerring]

This is most likely your issue then. Do not directly connect the MX together. Have them connect to the same L2 and let VRRP do its job.

[superfly]

So I've tested it all and what is on the image below is exactly what happens. The wired connection is always preferred over the cellular connection.

I also tested this without a L2 switch. To set up the HA pair you have to directly connect both MX's together. VRRP then works to have a Master and Passive. Then everything works the same no matter which MX I plug into (unless of course the MX I've plugged into looses power).

Thanks for all the assistance!

Here's the image again for reference.

[NolanHerring]

Thanks for the update and glad you got it figured out 😃