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

[Hannes Gredler]

hi richard,

guessing the "correct" export metric of a direct route
is a bit of philosophical question ;-) - let me explain:

since JUNOS does not know which end(point) of the subnet you are
interested in, it advertises the worst case, which is the cost
to reach the far-end, the cost of "crossing" the interface.

for loopback interfaces (which do not have a notion of far-end)
the "local" cost (0) is advertised.

HTH,

/hannes

Richard A Steenbergen wrote:
> Question about the default metric of a route being redistributed from 
> directly connected to isis...
> 
> Router A is connected to Router B (both Juniper) via a single link which
> has an isis (level 2 only) interface metric of 10 on both sides. The
> loopbacks are injected into isis via an interface passive command with
> explicit metric of 0. Router B has an interface which is being
> redistributed into isis using an export policy like so:
> 
> term DIRECT {
>     from protocol direct;
>     then accept;
> }
> 
> But the observed metric value from router A on all of the routes being
> "redistributed" in this way from router B is 20, even though the
> interface metric between routers is only 10. The loopback route (which
> isn't redistributed) has a correct value of 10. A show isis database
> detail confirms that the other routers are receiving the "redistributed"
> route with a metric of 10 before adding interface costs. After playing
> around with it for a bit, I was able to reset this to 0 by changing the
> above redistribution to:
> 
> term DIRECT {
>     from protocol direct;
>     then {
>         metric 0;
>         accept;
>     }
> }