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

[Ben Dale]

Hi Skeeve,

On 18/10/2012, at 10:04 AM, Skeeve Stevens <skeeve+junipernsp at eintellego.net> wrote:
> Question is.... the specs say it can support a maximum of 700k routes.
> 
> Now, if what I suspect is right, that is great, but I am getting
> conflicting information.
> 

The way I read the data sheets is the maximum "supported/tested" in forwarding table is 700k.

> A full feed at the moment is about 430k routes.  So I am hoping that the
> SRX550 could take multiple full feeds... lets say - 3-4, and it just
> installs a single unique copy of the full feed which is way under the 700k
> threshold.
> 

That is correct.  The advertised values are referring to supported/tested FIB, whereas RIB will hold as much as you have memory available (within reason).  

> But someone was trying to tell me that it couldn't take two world feeds as
> together they are 860k routes.. but my gut feeling is that this is wrong as
> I am not sure what purpose the SRX550 having 700k route capacity would be
> if it operated that way.

This is simply not true - I have a customer whose SRX100H is taking one full view (though data sheet says 8K), and another with an SRX240H with 3 separate feeds and no issues.  

Where you will come unstuck is if you start dumping each feed into separate VRFs, then you'll start burning more FIB, and as always the infamous KRT queueing "feature" can bite you during fail-over (though I have to say I don't see it on SRX/J all that often).

Here's what a J6350 with 2GB of memory looks like with 3 feeds (this is an old snapshot back when the DFZ was ~350k):

Groups: 2 Peers: 3 Down peers: 0
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
inet.0           1056579     354871          0          0          0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
x.x.x.x         yyyyy     322391       3804       0       6     1:24:31 143268/353090/353090/0 0/0/0/0
x.x.x.x         yyyyy      86256        192       0       2     1:24:32 2/353091/353091/0    0/0/0/0
x.x.x.x         yyyyy     125597      13456       0       0  4d 4:56:06 211601/350398/350398/0 0/0/0/0
 
Only "active" routes are installed in FIB - the rest sit in RIB.  Here's what memory usage looks like for the above:

> show chassis routing-engine
Routing Engine status:
    Temperature                 26 degrees C / 78 degrees F
    CPU temperature             45 degrees C / 113 degrees F
    Total memory              2048 MB Max  1044 MB used ( 51 percent)
      Control plane memory    1472 MB Max   618 MB used ( 42 percent)   <--- RIB sits here
      Data plane memory        576 MB Max   420 MB used ( 73 percent)   <--- FIB sits here
    CPU utilization:
      User                       0 percent
      Real-time threads          9 percent
      Kernel                     0 percent
      Idle                      91 percent
    Model                          RE-J6350-3400

Also, when using SRX, make sure all your peers are in the same security zone to handle asymmetry issues that may arise.

Ben