[j-nsp] MX104 capabilities question

Saku Ytti saku at ytti.fi
Tue Jun 7 02:01:57 EDT 2016

On 7 June 2016 at 03:09, Ross Halliday
<ross.halliday at wtccommunications.ca> wrote:


> The MX104 is a great value box, but lacks some features which make it a "big boys" router. Aside from the RE, the control plane isn't as segregated as I thought, leading to interesting bugs like PR1031696 - which caused me to briefly lose all 10G optics in the entire chassis while installing an XFP; as well as some irritating behaviour from the ddos-protection mechanism. The larger chassis are *sort of* like running DFC cards in a 6500, were forwarding operations are pushed down. MX104 entirely relies on an integral system in the chassis and all you install are MICs, *sort of* like running a module with CFC and relying on the SUP.

I don't see how this makes it any less of a box, in my mind this makes
it superior box. You lost single PFE/linecard, which happens to be
only linecard you have.
In my mind fabricless single-linecard design is desirable, as it
reduces delay and costs significantly. Not only can you omit fabric
chip, but you can get >2x the ports on faceplate, as no capacity is
wasted on fabric side.
Because of this design choice, I think MX80/MX104 is better box with
smaller BOM than ASR9001.

Regarding PR1031696, years ago I had bunch of 3rd party SFPs which
would crash MX PFE. I practically begged JTAC to fix it. The issue was
caused by SFP being sluggish to answer to I2C polling, and the code
which was expecting an answer crashed when it couldn't receive I2C
answer fast enough. I tried to explain to them, it's only matter of
time before original SFP develops I2C error, at which point you'll see
this from customer buying 1st party optics. JTAC was unconvinced, told
me to re-open if I see it on 1st party.
I used many channels to complain, but no avail. To me this was
absolutely appalling and short-sighted behaviour.

But all platforms can have all kind of problems, and if you would have
multiple linecards, sure, in this case you'd only crash one of them.
But just having multiple linecards won't help that much, you can still
crash all linecards due to RE problem, so you're still going to need
second router for proper redundancy, at which point it becomes
immaterial if you have this 'linecard redundancy' or not.

More information about the juniper-nsp mailing list