I have 2 MX devices (warm spare) and 3 switch stack (MS, physically stacked with stack cable).
Do I need to enable Link Aggregation on stack connected to MX (to aggregate 3 ports)?
At the moment 1 ports from every switch is connected to 1 MX and same for a 2nd MX. On every MX 3 LAN ports are used for switches. STP is disconnecting 2 (as it should I believe), meaning only 1 port is active at given time.
If I need, how to enable LACP on MX as I see no option to do so? And to my knowledge it should be done on both sides for link aggregation to work (maybe...? 🙂 )
Bear in mind that (somewhat model-dependent) your MX is probably unlikely to be able to process the load from a whole bunch of high-capacity links anyway, particularly if you have Advanced Security and/or VPN functions running. If it's a 'big' MX (250? 450?) then the bottleneck probably moves to your Internet link(s), so those high-capacity uplinks will likely be under-used. If a large proportion of your traffic is east <-> west, then you're probably best with an aggregation switching layer and routing there (in ASIC)
I'm sorry but using the high capacity traffic is not the main reason why we would want to use lacp port channels on the MX.
We need port channels on MX for a more stable spanning-tree setup. Since the MX does not support STP which is actually should we have to rely on the bounced back STP messages coming from the switch to have the higher portnumber blocked.
I would much rather have the MX at least support STP and even better support LACP so the MX natively takes care of those layer 2 messages to have a more stable topology.