High CPU on MAX Transit

I’ve done some searching on this topic, but all the posts seem to be from 5+ years ago.

When I’m transferring data at high speeds, (50+mbps) on the cellular modem, I’m seeing CPU spike up very high. Usually it hits 90-100%.

I’ve also checked to see what the speeds are on my local network and it appears that the MAX Transit can only do ~350mbps through the WAN interface and about ~600mpbs on the LAN. Kind of shocked here.

I had PepVPN connection enabled, so I disabled it thinking that might be part of it. It didn’t make a difference with it disabled.

I don’t have any special routing or firewall rules.

I have tested this wired and wireless, with similar results on both.

I’ve yet to try a wired WAN connection, but just checking to see if this is normal.

Router throughput is specified as a max of 400mbps on the Transit. So your ~350mbps wan to Lan is about right.

I’ve never done a speedtest Lan to Lan on any install I’ve done in the past as the transit has always sat at the edge and there have been other switches Lan side so I’ve got no reference to know if 600mbps is expected or not

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Thanks Martin. I now recall seeing that on the spec sheet. Seems odd to put a CAT18 modem in something that’s limited to 400 mbps on the firewall side. I suppose that some may just do passthrough?

It was originally released with dual LTE-A modems - so a theoretical max 300Mbps down and 50Mbps up (CAT6) - hence 400Mbps. However no one I know has ever managed to find 300Mbps down on LTE-A in the real world.

The same will likely be said for CAT18 modems - for the moment at least, so at this price point and size especially, the Transit CAT12 Dual / CAT18 Single, pretty much hits the sweet spot for me.

In tests (Three and EE in the UK mainly), the extra frequencies and additional carrier aggregation of the CAT18 version provide more reliable and often lower latency connectivity and faster speeds - but nowhere near the limits of the Transit in any of the locations I’ve been testing.

Deep in the centre of London - where you’d expect more bandwidth availability generally (but there is more noise as they are thousands of cells), the CAT18 does especially well for fixed location installs (even then though contention means we’ve never seen more than 250Mbps), but when we need proper reliability (vehicles or humans in motion) we use the dual CAT12 and fill all the four SIM slots with a mix of networks.

As with anything in life its a question of balance. The HD2 MBX can do 2.5Gbps of throughput, and the EPX can do 30Gbps but they are physically bigger and course more expensive.


Makes sense. I’m not going to be “needing” over 100 meg really anyways. Good to know that there is a benefit in the CA and 4x4 MIMO. Thanks.