[j-nsp] network engineering

[Peter E. Fry]

----- Original Message -----
From: Mark Tinka <mtinka at globaltransit.net>

> On Friday 06 February 2009 05:09:30 pm Matthias Gelbhardt 
> wrote:
> 
> > We have asymmetric routing in several cases. I would
> > like to know, how you would deal against that?
> 
> The moment you're multi-homed to the Internet, asymmetric 
> routing is a fact of life; and it's not really a bad
> thing. [...]

  To add to that: Are you keeping state somewhere? 
Asymmetry does not affect stateless behavior; control (i.e.
"confine to where appropriate", usually) your statekeeping
and you won't have a problem either.
  Funny thing I noticed (knew about, but never thought much
about) when I set up my SSG for failover -- I'm accustomed
to devices that forward statelessly even when keeping state
for filtering purposes.  ScreenOS checks flows before it
routes, so it forwards responses out the zone (thinking
about it, I haven't checked to see if it keeps flow state
per-interface when the zone contains multiple interfaces) on
which the request arrived.  When it's necessary, it makes
for a simpler config.  I'll have to look into JunOS+ES to
see if it operates similarly.

Peter E. Fry