Juniper SR300 maximum BGP routes

Question

I've got a Juniper SRX300 which i'm using to connect to 2 BGP peers. The documentation i've read says this SRX only supports 300,000 BGP routes, so for each peer I created an import policy (based on communities) to only accept my peers customer routes and not the full table. These are roughly 2k routes for peer 1 and 3k routes for peer 2.

It all works fine, however it seems that although only the filtered routes are used the entire table is being stored. For example if I do this I get details of any route from the full table(s)

show route 1.1.1.1 hidden detail

inet.0: 726648 destinations, 726650 routes (3915 active, 0 holddown, 722735 hidden)

1.1.1.0/24 (1 entry, 0 announced)
 BGP                 /-101
        Next hop type: Router, Next hop index: 1333
        Address: 0x1990fe0
        Next-hop reference count: 728538
        Source: X.X.X.X
        Next hop: X.X.X.X via ge-0/0/6.0, selected
        Session Id: 0x0
        State: <Hidden Ext>
        Local AS: XXXXX Peer AS: XXXXX
        Age: 4:40:08
        Validation State: unverified
        Task: BGP_XXXXX.X.X.X.X
        AS path: XXXXX 13335 I
        Aggregator: XXXXX X.X.X.X
        Communities: XXXXX:XX XXXXX:XXX XXXXX:XXXX XXXXX:XXXX
        Localpref: 100
        Router ID: X.X.X.X
        Hidden reason: rejected by import policy

So my question was, is the 300k limit only on active routes? Or stored but hidden routes as well?

Thanks

Answer 1

The route table stores all received routes (from your peer). The forwarding table only stores those routes accepted by policy.

The maximum size (256K routes) applies to each.

You may want to ask your ISP to filter for you.

Answer 2

The SRX3xx data sheet shows both the SRX300 and the SRX345 having 4GB of memory, but their RIB scale being 256K and 1M routes respectively:

https://www.juniper.net/assets/us/en/local/pdf/datasheets/1000550-en.pdf

These usually just marketing numbers based on the maximum number that has been officially tested, with the test being based on the target segment for the platform - as you can see from your output, there are no hard limits on the RIB, so I would expect you would have no issues storing up to 1M routes in RIB on an SRX300.

With FIB (forwarding plane, or active routes) the story is very similar: being 256K and 600K respectively - since these lower end SRX3xxs emulate forwarding hardware in software, I don't think you'd have any issues with 600K active routes on the lower end box either (eg: there would be no hardware/TCAM limits), however since the global table is somewhere in the low-mid 700Ks these days, this still wouldn't be enough to hold a full view in FIB.

Bear in mind that the CPU of these lower-end boxes is quite limited, so loading routes, doing path calculations and installing into "FIB" will be quite slow on reconvergence as you increase your prefix count.