MX85 Warm Spare config with Tertiary Uplink

[Steve-Potter]

Currently I have dual diverse fibres to the building each to a router with a /29 subnet on presented on ports 1 & another /29 subnet on port2. in an Active / Active configuration.

All 4 ports connect to a layer 2 switch and from this switch is connected the primary MX85 with WAN ports 1 & 2 configured the same as the router ports in load balance mode.

The MX85 is connected to the switch stack via two LAN ports

I want to add a warm spare MX85 to this network, and would use the MX Uplink IP method. My ISP is adding a third /29 subnet on Port 3 of the routers, and documentation suggests I can configure WAN1 of the warm spare to this subnet. (Gamma share all 3 subnets across the two fibres) 

Have I understood this right and is this the correct configuration?

[PhilipDAth]

That will work.  Note that the third /29 on the warm MX won't be used unless WAN1 and WAN2 fail on the primary MX.

Is there a reason you can't put WAN1 of each MX into the first /29, and WAN2 of each MX into the second /29, and not bother with a third /29?

[Steve-Potter]

Hi

If that is an acceptable config then that would work for me, saves paying fo the additional IP block. (which I had to put on hold anyway due to a change freeze).

Steve