Hi Peter, hi all,

to iterate on the comment I made on the mic a few minutes ago, I
apparently have a rather different understanding of existing IS-IS
behaviour.  Reading 5305/5308,

...                     "if a prefix is advertised with a metric larger
   than MAX_V6_PATH_METRIC (0xFE000000), this prefix MUST not be
   considered during the normal Shortest Path First (SPF)
   computation."

A prefix that is "not considered" is not an unreachable prefix.  It's a
prefix that is in the DB but ignored entirely, as if it wasn't there at
all.  A less specific prefix may cover it, and I would expect that to
work normally.

The UPA draft is changing this such that now some values may mean that
the prefix is in fact unreachable.  I'd rather not do that and just add
a sub-TLV for it.

(Alternatively, if I misunderstood 5305/5308 - I'm pretty sure I'm not
the only one to read it that way and that's a pretty important
errata?!?)

Cheers,


-David

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