[j-nsp] MX204 vs. MX240??

[Rob Foehl]

I'll preface this by saying that the MX204 is a great box, and fits many a 
niche quite well...  However:

On Fri, 8 Nov 2019, Clarke Morledge wrote:

> My understanding is that the MX204 is a 1 RU MPC7, but with a few 
> modifications.

More or less -- it's an RE glued to the non-fabric-facing parts of the 
MPC7, which tends to tickle some "interesting" corner cases in code that 
assumes there's a fabric chip present.

> I understand that the eight 10Gig ports have been modified to 
> allow for 1 Gig transceivers as well, and perhaps that the QSFP ports can 
> accommodate a pigtail for providing a bunch of 1 Gig connections, if 
> necessary.

You can run 1G optical transceivers in the 8x SFP+ slots, if necessary...

Don't.

Seriously, don't.  The initial code in 17.4 refused to light them at all, 
and seems to have been haphazardly gutted of all config/op statements 
related to 1G optics.  18.1R3 is necessary to support them at all, and 
they show up as xe- interfaces only, half the config is hidden and the 
other half refuses to commit, they have a lot of weird problems with rate 
negotiation, and they don't work in bundles unless you really beat on the 
other end to convince it to bring up the aggregate.

Just pair the 204 up with a cheap switch...  Whether you want to get crazy 
and run Fusion is another matter.

> Also, I understand that the MX204 CPU and other resources are a vast 
> improvement over the MX80, and that the MX204 can handle multiple full 
> Internet route BGP feeds, just as well as the MX240 REs can, without 
> compromise in performance.

Yup, plenty of memory and CPU to play with, it'll do 10M routes without 
batting an eye.

> The newer VM support inside the RE makes the requirements for an additional 
> RE less important now, according to my understanding.

Again more or less -- ISSU between VMs works reasonably well, but Juniper 
has walked back the original claims of "never needing to upgrade the 
hypervisor" quite a bit since these were released.  I've been doing full 
vmhost upgrades every time to minimize surprises.  Need a pair for real 
redundancy, anyway...

> So, if you do not need a lot of speeds and feeds, and can live without a 
> physical backup RE, the MX204 would be a good alternative to a MX240.

You'll also need to be willing to run relatively recent software if you 
want to do anything beyond basic layer 3.  I had 3 MX204-specific PRs on 
18.1R3 that led to running 18.4R1-S4 now -- and have 5 new SRs open 
against that code.  Your mileage may vary...

-Rob