Clean up dynamic names

Wed Feb 8 20:04:54 UTC 2017

On Wed, Feb 8, 2017 at 1:09 PM, Cuttler, Brian R (HEALTH) <
brian.cuttler at health.ny.gov> wrote:

> Kevin,
>
> I understand. Let me refocus the question.
>
> DHCP:
> I know DHCP will remove the info when the old lease expires, will it
> remove this information for me in the case of the device falling off line,
> and how can I accelerate that process so that I can reassign the printer
> tag to a new IP address.
>
> BIND:
> Knowing that I have a "A", "TXT" and "PTR" record, is # nsupdate the
> correct mechanism, and how do I specify the commands to remove the "TXT"
> record as it is missing column 1 in the tables. I have previously manually
> both created and removed forward and reverse records, but text records are
> different, I just don't know how different.
>
> The forward table looks like this
>
> hr16038                 A       10.57.48.209
>                         TXT     "00f8e5793e94da14990f27763448c54a00"
>
>
If the first field is shown as blank, it means "same as previous", so
"hr16038" in this case.
If the ttl is not shown, it is "same as last $TTL record"  (or taken from
'minimum' field in SOA if no $TTL)
If no class is shown, it is probably "IN", I forget now where it defaults
that.
If the first field is not fully qualified, the domain is taken from the
last $ORIGIN, or SOA?, or named.conf.
So the records if listed in full would be something like:

hr16038.somedomain.tld.    9999   IN       A       10.57.48.209
hr16038.somedomain.tld.    9999   IN    TXT     "
00f8e5793e94da14990f27763448c54a00"

nsupdate is probably the best tool for removing the old records.

-- 
Bob Harold

> Thank you,
> Brian
>
> > -----Original Message-----
> > From: bind-users [mailto:bind-users-bounces at lists.isc.org] On Behalf Of
> > Darcy Kevin (FCA)
> > Sent: Wednesday, February 08, 2017 12:58 PM
> > To: Users of ISC DHCP <dhcp-users at lists.isc.org>;
> bind-users at lists.isc.org
> > Subject: RE: Clean up dynamic names
> >
> > ATTENTION: This email came from an external source. Do not open
> > attachments or click on links from unknown senders or unexpected emails.
> >
> >
> > Honestly, this is like asking for a closet that automatically throws out
> > the items you pitch into it, once the items are deemed obsolete or junk.
> >
> > The DNS database is a repository of information, like a closet, but it
> has
> > no inherent way of knowing the value or currency of the information that
> > is put into it. Therefore any "auto-cleaning" mechanism is going to be
> > unreliable, at best.
> >
> > Now, if you want, you can add "metadata" alongside your regular data, or
> > in a parallel database, e.g. a timestamp or something like that. You
> could
> > then use that "metadata" to make decisions on what to delete. Various
> > layers on top of DNS itself can perform "aging" and "scavenging" in this
> > way (Microsoft's solution does this). But that's not perfect either --
> > we've had major infrastructure outages due to erroneous scavenging of
> > Microsoft-hosted DNS data.
> >
> > The bottom line is that the processes which read and write data into/out
> > of the DNS database are responsible for keeping track of it, evaluating
> > it, and getting rid of data that is no longer needed or wanted. This is
> > not something the database itself can do.
> >
> >
> > - Kevin
> >
> >
> >
> > -----Original Message-----
> > From: bind-users [mailto:bind-users-bounces at lists.isc.org] On Behalf Of
> > Cuttler, Brian R (HEALTH)
> > Sent: Wednesday, February 08, 2017 11:59 AM
> > To: Users of ISC DHCP; bind-users at lists.isc.org
> > Subject: Clean up dynamic names
> >
> > Hello Bind and DHCP users,
> >
> > Sorry for the post to both lists, but it is a dynamic DNS question and
> I'm
> > not sure where the answer will come from.
> >
> > We replaced the network card in a printer, which had been working, we had
> > a DHCP lease, we had created from DHCP a dynamic DNS forward and reverse
> > record for the printer.
> >
> > The new network card was configured to provide the same HOSTNAME
> > information as the old card, we do this because the printers now carry
> > network names that reflect their inventory tags.
> >
> > I need the cleanest/best way to remove the old DNS records so that the
> > DHCP server will be able to register the IP information in DNS.
> >
> > Needless to say the TXT fingerprint information for the two network cards
> > is different, so automatic cleanup, which would say, allow us to rename
> > the printer if needing the same network card, will not work.
> >
> > I suspect that # nsupdate removing the A, TXT and PTR records is the way
> > to go, but hope for a quicker, less error prone method.
> >
> > Thanks in advance,
> > Brian
> >
> >
> >
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