Static vs SLAAC - Static expected to be preferred?

[Benedikt Stockebrand]

Hi Mark and list,

Mark Smith <nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org> writes:

> Suggested rule -
>
> Rule X: Prefer greatest preferred lifetime
>    If the addresses SA and SB both have non-zero value preferred
>    lifetimes (are "non-deprecated"), prefer the address with the
>    greatest value preferred lifetime."

unless I'm mistaken this implies that in a setup with multiple
advertising routers a host will choose the source address (without an
explicit bind(2) in the client side application) according to the
advertising router the host has last received a router advertisement
from when initiating a TCP connection.

First off: In most practical cases I'd consider it good practice to
have all routers advertise all prefixes for a subnet in a consistent
manner, and in these cases the extra rule doesn't have any effect
unless the lifetimes advertised are explicitly configured/manipulated;
this appears to be fine with me if there's some benefit elsewhere from
adding this rule.

But: In the---to my understanding more unusual---case where different
routers advertise different prefixes, the behaviour will however be
affected, possibly causing some "sometimes it works, sometimes it
doesn't" behaviour that is rather tedious to track down and fix.

So your proposal may have some serious side effects.


Cheers,

    Benedikt

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Benedikt Stockebrand, Dipl.-Inform.   http://www.benedikt-stockebrand.de/