[j-nsp] How are max routes calculated on an SRX

[Ben Dale]

On 18/10/2012, at 2:05 PM, Jeff Wheeler <jsw at inconcepts.biz> wrote:

> On Wed, Oct 17, 2012 at 8:38 PM, Ben Dale <bdale at comlinx.com.au> wrote:
>> Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
>> inet.0           1056579     354871          0          0          0          0
> ...
>>      Data plane memory        576 MB Max   420 MB used ( 73 percent)   <--- FIB sits here
> 
> It's probably worth applying some simple arithmetic.  The DFZ today is
> 20% larger than in Ben's snapshot, above.  Data-plane memory use
> obviously doesn't scale linearly with the number of routes, but it it
> did, his memory use today would be ~88%.

Right - this is one of those things I've been wanting to sit down and lab out for a while, but using some very unscientific process (and without any inet.6), it doesn't appear to come anywhere close to linearly scaling:

An SRX I just happen to have on the desk in front of me, is using 274MB of Data Plane memory with nothing more than a handful of routes installed.

Again *very* rough numbers puts the ~340K of v4 paths in at ~154MB (420MB from previous example minus 274MB of an SRX running at virtually idle).  Add 20% for today's DFZ and we're looking at around ~185MB

As an aside, adding more RAM to SRX/J does very little percentage-wise to the available data plane memory.


> If I had that box deployed today, I would plan to upgrade it when
> needed.  If I deployed it as a new device today, I would expect to be
> fired.


That's all well and good, but there is an awful lot of *current* branch/enterprise hardware running just fine with these limitations - and until all (or ANY) enterprise routing platforms (not just Juniper) start shipping with 64-bit-capable OSs and 4GB+ memory as an option there will be a lot more of these conversations being had.  Not every enterprise can justify the big shiny tin.

I should step back and say that I'm not condoning the use of under-powered kit (and you sure won't be getting any support from Juniper running this hot), I'm just highlighting what I have seen in the field ; )

Ben