HA MX250 pair with temporarily mismatched LAN connections

[Pugmiester]

Hi all,

We're in the middle of a switch migration project and I hadn't considered how best to get the MX LAN links moved over. Our setup is a little unconventional, in that the appliances are sat in different buildings and subsequently connected to differnet LAN switches, but each using port 9 on the MX with a matching set of MX and switch port VLAN config.

What I'm hoping to be able to do, is configure Port 19 (SFP+ 10Gb) with a matching VLAN setup and then migrate the LAN connection over on each appliance. In a perfect world, we would have multiple pairs of local hands around to do this simultaneously, but it's more likley I'll be on my own.

I should clarify that the old and new switches are currently trunked together so communicatiosn between the MX's over the LAN link will still be possible once the connections are moved to the new switches.

Am I likely to give the MX's a headache by having different LAN ports in use on the Primary and Spare MX, even if it's only for 15 minutes while I run between buildings?

[alemabrahao]

I don't see any reason for it to cause a problem, if I'm not mistaken, I've done migrations this same way running two MX at the same time and didn't have any issues.

[Pugmiester]

Thanks for the quick reply. I was reasonably sure things would be OK, but it's Friday and my brain is frazzled after a busy week so figure a second opinion would be wise.

[RWelch · Accepted solution]

You should be OK as long as these conditions are met:

Both MXs can reliably communicate with each other over the LAN (VRRP heartbeats must pass between them).

The VLAN configuration matches on both MXs and the connected switches.

The switches (old and new) are trunked together, ensuring the MXs remain in the same broadcast domain and can see each other on all VLANs.

[Pugmiester]

Thanks for the quick reply. I was reasonably sure things would be OK, but it's Friday and my brain is frazzled after a busy week so figure a second opinion would be wise.

I'm certainly not making any changes today, but I feel much more confortable now to get something planned in for next week.

[PhilipDAth]

I have done exactly this, but permanently.

The primary site had plenty of 10Gbe switch ports, so I used those.

The DR site didn't, so I used a Gigabit port on the switch.