[c-nsp] how many IGP routes is too many?

[Saku Ytti]

Hey,

> is there any recent study about how many IGP (isis or ospf, I don't
> really care right now) routes are "too many" with current generations of
> route processors? Think RSP880, NCS55xx and so on on the cisco side and
> PTX1000, PTX10002, etc on the juniper side.

SPF complexity doesn't scale with routes, routes are leaves to the
node. You can approximate complexity with O(ElogN) where E is edges
(links) and N is nodes (routers). I've done this before IGP migration
and got net1 and net2 complexity numbers separately and with summed
edge+link counts, got relative difference between summed and separate
and multiplied  SPF time with the relative difference number to get
estimated migrated network SPF aggregate time, and it's been spot-on.

At any rate tens of thousands of routes is fine and normal, but if
you'd try in a lab, I'd not be particularly surprised if millions
work. Of course you should not really want to carry anything else but
loop0 and NMS networks in IGP.

-- 
  ++ytti