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

Richard A Steenbergen ras at e-gerbil.net
Tue Mar 3 08:42:22 EST 2009

On Mon, Mar 02, 2009 at 11:14:40PM +0100, Hannes Gredler wrote:
> much more simple - the default IS-IS metric for any interface
> (i.e. if you do not have reference-bandwidth configured) is 10.

Except that I'm seeing some interfaces with an isis metric of 5 or 3, 
which is the root of the entire problem (inconsistent costs). if they 
were all set to 10 I wouldn't have noticed. :)

The reference bandwidth I have configured doesn't match up with these 
results either. I'm using 100g (the max possible value), to create a 
high metric incase anyone ever accidentally left off a metric, so the 
metric on a 10g interface there would be 100 not 10.

> http://www.juniper.net/techpubs/software/junos/junos94/swconfig-routing/modifying-the-interface-metric.html#id-11111080

I saw that page, but honestly I would never have interpreted anything on
there to mean "interface ROUTES being exported INTO isis" rather than 
the more conventional "isis speaking interfaces". And infact it can't 
be, or it would have been affected by reference bandwidth as mentioned 

> | And maybe throw in c) ae bandwidth
> | changes should auto-update the cost, and d) the reference-bandwidth
> | should be configurable, for good measure. :)
> i am not sure what you mean with c) 

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.

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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