[c-nsp] Link State Periodic SPF

[Dhamija Amit]

Hi Oliver

Just a small doubt default maximumLSPGenerationInterval is 15 mins & so is SPF run . If we fine tune our maximumLSPGenerationInterval to 65000 secs i.e 1083 mins , Still my ISIS SPF Periodic will be 15 mins ??

(lsp-refresh-interval set to 65000 and max-lsp-lifetime set to 65535).

Thanks,
Amit


--- On Fri, 1/11/13, Oliver Boehmer (oboehmer) <oboehmer at cisco.com> wrote:

> From: Oliver Boehmer (oboehmer) <oboehmer at cisco.com>
> Subject: Re: [c-nsp] Link State Periodic SPF
> To: "Dhamija Amit" <amiitdhamija at yahoo.com>, "cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net>
> Date: Friday, January 11, 2013, 7:30 AM
> 
> 
> On 11/01/2013 03:02, "Dhamija Amit" <amiitdhamija at yahoo.com>
> wrote:
> 
> >Hi 
> >
> >I would like to know about Link state Periodic SPF's , I
> have seen in
> >Cisco IOS-XR and Juniper M/T -Series ( Junos) by default
> Periodic SPF
> >runs every 15 minutes.
> >
> >Going to concept of SPF whenever there is change in
> topology router runs
> >SPF based on SPF interval configured. Also when LSP/LSA
> refreshes after
> >certain period then during that time also router
> executes SPF's.Then what
> >is the purpose of periodic SPF's . Can we disable the
> same , What kind of
> >impact will be there ??
> 
> ISIS standard (7.3.18) asks for at least one SPF every
> maximumLSPGenerationInterval (which is, by default 15 mins).
> On today's
> routers, SPF takes a few msecs, so there is not concern
> running this every
> 15 min.. XR allows to disable the period SPF
> (privileged/cisco-support
> "spf periodic disable" command in ISIS AF mode), but I don't
> see a reason
> why someone would need it.
> As far as I know, a refreshed LSP does NOT trigger an SPF
> unless it
> contains changed topology information.
> 
>     oli
> 
>