[j-nsp] juniper router reccomendations

[Tore Anderson]

* Mike <mike+jnsp at willitsonline.com>

>      Im in a colo in one location (A), and have a private 1G ethernet
> to another geographically distant colo (B). Each colo has a different
> ip transit provider and I am advertising my own prefixes. At colo A I 
> receive a subset of Internet routes internal to that provider, while
> at colo B I get full tables. Id like to like to exchange routes
> between Colo A & B for better routing as well as for failover in the
> event I lose ip transit at either location.

You don't need full tables for failover, getting a default from each
provider will do fine for that purpose.

However, what you could do with a cheaper device with limited FIB space
is to take full feeds but be selective about which routes you download
into the FIB. In JUNOS, you can control that with "set routing-options
forwarding table export FOO".

The assumption here is that you really don't care which transit provider
is used for the odd packet destined for Timbuktu. So you can let those
follow a default route to the colo-local provider, instead of wasting
valuable FIB space on them.

The routes or ASNs you do care about (i.e., the ones where you want
nodes in colo A to cross your backbone link to colo B or vice versa,
instead of exiting through the local transit), those you can
selectively ensure get installed into the FIB. You could do so with
static config, or you with a little more effort use flow telemetry to
dynamically figure out, e.g., your top-10k destination routes and
install those.

If you insist on a router with a big FIB, expect to pay more for it,
much much more. Keep in mind, though, that in all likelihood you will
probably (almost) never send any packets to 95%+ of the prefixes that
will be occupying your big and expensive FIB.

Tore