Well, longest prefix match is kind of useful in some scenarios i think.
Imagine a site that is multihomed to two ISPs and has two PA address blocks.
Now, longest prefix match ensures that when a node of the multihomed
site wants to contact any other customer of its own isps, it does
perform the correct source address selection and that is likely to be
critical for the communication to work, especially if the isps are doing
ingress filtering (i am assuming that the intra site routing of the
multihomed site will preffer the route through the ISP that owns the
prefix contained in the destiantion address)
Even though this is one case and the problem is more general, i tend to
think that this is an importnat case and things would break more if this
rule didn't exist
Mark Andrews escribió:
This rule should not exist for IPv4 or IPv6. Longest match
does not make a good sorting critera for destination address
selection. In fact it has the opposite effect by concentrating
traffic on particular address rather than spreading load.
I received a request today asking us to break up DNS RRsets
as a workaround to the rule. Can we please get a errata
entry for RFC 3484 stating that this rule needs to be ignored.
IETF mailing list