[AusNOG] Routing in NX-OS vs IOS

[Glen Turner]

Ben wrote:
> ....but wait!  I have multiple protocol clients using the same route-map - and maybe I *don't* want the change to be propagated to all of them at once as soon as I type "exit".  The way IOS allows you to change a route-map, then cause it to take effect on a per-peer basis via a soft clear, is operationally *useful*.

It doesn't work that way. Changes to route-maps in IOS occur incrementally as typed. That's a major pain if you have a high ongoing rate of incoming BGP changes, as some of those incoming routes will meet a routing policy which is not either the new policy nor the old policy. That makes it essential to "clear .. soft in" each neighbour after a route-map change to regain a reasonable policy for all routes. Imagine changing an IOS route-map at a router connected to a peering point and you'll see what a PITA that is, especially when compared with how nicely JUNOS does the same thing.

The only reason you see the "reasonable" behaviour you do is because you don't have a high rate of incoming route changes whilst you are altering the configuration.

> ...great - so now whether or not I type "exit", 60 seconds after I typed a command it will take effect...?  And this behaviour is documented only for the 7k, not the 5k? 

Does that behaviour still occur if you say "configure session ..."? In any sane world nothing would change until the "commit".

- glen