[c-nsp] OSPF fast convergence on Sup32/SXI

[Ben Steele]

You can try OSPF fast hello's but the general consensus is to not use them
purely because there is no pseudo preemption for it(unlike bfd) so if you
have a busy router, or even a router with bursty busyness aka snmp polling
you can draw false positives into your fast hello's.

Having said that something like 2 sec hello with 6 sec dead timer has worked
well for me before, you could try cutting that down to 1 and 3 respectively,
it's probably just a matter of test and tweak and see what works for you.

If you can work a solution that incorporates BFD you will be better off in
the long run(as your router certainly won't get less busy as time goes on)
if the ultimate goal is fast convergence with 5 exclamation marks :)

Ben

On Sun, Aug 30, 2009 at 12:45 AM, Gert Doering <gert at greenie.muc.de> wrote:

> Hi,
>
> for a new project, I have been tasked to build a network that does
> IGP fast convergence "as fast as possible!!!" (with 5 exclamation marks).
>
> Due to other reasons (... of course this needs to be FAST and cost
> NOTHING...), the routers will be 6504+Sup32s, planned IOS is SXH3a or
> SXI2.
>
> BFD won't be possible, as routing will be done on SVIs (thanks, Cisco)
>
> [*maybe* I can do this on port-channel dot1q subinterfaces, but I'm not
> yet sure how this will work out - can MUX-UNI be used to mix routed
> subinterfaces and switched VLANs?  I've only used it to mix MPLS subfs
> and switched VLANs].
>
> Now I'm looking for experience and recommendations about tweaking OSPF
> - how far have you (successfully) reduced OSPF hello timers?   Any other
> success or horror stories about IGP fast convergence on Sup32?
>
>
> ... and yes, I'm aware that I won't be able to do "sub-500ms" on this
> platform.  I'm not aiming for this :-) - something like "< 3s" would
> be perfect, "< 10s" would make $them grumble, but eventually accept it...
>
> gert
> --
> USENET is *not* the non-clickable part of WWW!
>                                                           //
> www.muc.de/~gert/ <http://www.muc.de/%7Egert/>
> Gert Doering - Munich, Germany
> gert at greenie.muc.de
> fax: +49-89-35655025
> gert at net.informatik.tu-muenchen.de
>
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