Quick question about Host records

[Jim Reid]

>>>>> "Bill" == Bill Moseley <moseley at hank.org> writes:

    Bill> Maybe it's too early for me as I'm not following your point
    Bill> below.  Could you clarify?  I'm not clear if the "potential
    Bill> problem" you mention is a result of having two name servers
    Bill> names share the same IP, or by having NSI automatically
    Bill> change the name of name servers so there's only one unique
    Bill> name per IP number.

The problem is what happens if there are two different names for the
same IP address and that IP address changes? So one of the names could
be updated to the new address while the other is left dangling,
pointing at the old address. Normally this doesn't matter much. One
name is right and the other is wrong. Big deal. But if the multiple A
records are glue for zone delegations, there can be trouble because
the glue no longer points at a name server for some zone. So when name
servers lookup names in some zone, they send queries to the wrong IP
address. That can mean lame delegations or SERVFAIL errors: maybe even
making the zone unreachable. Perhaps this might be important.

Suppose you list ns.hank.org as one of your name servers, but this has
the same address as ns.jim.org, which is one of my servers. Maybe I'm
your ISP or I offer a slave DNS facility for hank.org as a favour. One
day I renumber ns.jim.org. When that happens the entry for ns.hank.org
in the .org zone would still point at the old address which might not
run a name server or even be in use any more. Now what if ns.jim.org
provides slave DNS service for a lot of .org zones? Aside from the
tedium of getting all those delegations updated, what if I forget to
tell one of my customers or they fail to change their delegation
information? Does this clarify things enough?

If all that has to change in the .org zone is the address of
ns.jim.org, everything just works when I renumber that server.