[j-nsp] ISIS metric of redistributed directly connected routes

Richard A Steenbergen ras at e-gerbil.net
Wed Mar 4 17:37:23 EST 2009

On Tue, Mar 03, 2009 at 06:38:24PM +0100, Hannes Gredler wrote:
> Richard A Steenbergen wrote:
> >I found several instances of 10g interfaces with a metric of 10, 20g ae
> >interfaces with metric 5, 30g ae with a metric of 3, etc, but I also
> >found a 30g ae with a metric of 5. The only excuse I can come up with
> >for this behavior is something is being calculated with a reference 
> >bandwidth of 100g and the isis metric isn't refreshing if the ae 
> >bandwidth changes (i.e. another member is added to lacp). Of course it 
> >could be something completely different, but thats the only theory I 
> >have which fits the facts.
> this is my current interpretation:
> -you basically want the auto-bw knob to work when exporting
>  non-igp-if direct routes, plus you want the metric calculator
>  to also honor ae dynamic bandwidth information.

No, I expected non-igp-if direct routes to have a metric of 0 unless I
set something different, and was surprised when that wasn't the case. 
You're telling me that this behavior is actually a feature, but I can't
find any documentation to support the metrics I've observed, so I'm
wondering if something is actually broken here. The only explanation I
can reverse engineer from the numbers I've observed so far is a
hard-coded reference bandwidth of 100g + not auto-updating the metric
when an ae changes speed.

What I actually want was accomplished by setting metric 0 in the export
policy on direct routes, I'm just trying to help you guys figure out if
this is actually a bug and/or a documentation glitch to save the next
guy the trouble that I had. :)

> can you mark all the testcases with 'X'
> that appears to be broken in your setup ?

I'm completely ignoring igp-if interfaces, I manually set my metrics on 
those interfaces and I'm going to assume that auto-bw works correctly on 

What I CAN'T explain are the default metrics on non-igp-if direct
routes. I have a configured reference-bandwidth of 1000g, but after
checking about two dozen interfaces on my network I observed the
following default value behaviors:

* 10 on all of the non-igp-if 10GE interfaces I checked
* 5 on most of the non-igp-if 2x10GE AE interfaces I checked
* 3 on most of the non-igp-if 3x10GE AE interfaces I checked
* 5 on some non-igp-if 3x10GE AE interfaces that were probably initially 
  2x10GE AEs when the IGP came up.

This doesn't match the configured reference-bandwidth of 1000g. The only
thing it would match is a reference-bandwidth of 100g that doesn't
auto-update for AE members with dynamically changing bandwidth values. 

This might or not be the case, it's entirely possible that something
completely unrelated is causing these values and if I looked through
more interfaces I would find an exception to disprove the theory. But I
know for certain that neither "always set to 10" nor "always set to the
reference bandwidth" are correct. :)

Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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