Clean up dynamic names

Wed Feb 8 20:09:03 UTC 2017

Thank you Bob,

I have handled the A and PTR records before, and knew from prior DNS zone file work that the first field defaulted, just I guess some reluctance to “play” with live tables. I feel fortunate (at the times I’m not feeling frustrated) that # nsupdate does not seem to cause any side-effects and is happy to reject commands it doesn’t care for.

Thanks,
Brian

From: Bob Harold [mailto:rharolde at umich.edu]
Sent: Wednesday, February 08, 2017 3:05 PM
To: Cuttler, Brian R (HEALTH) <brian.cuttler at health.ny.gov>
Cc: Darcy Kevin (FCA) <kevin.darcy at fcagroup.com>; 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.

On Wed, Feb 8, 2017 at 1:09 PM, Cuttler, Brian R (HEALTH) <brian.cuttler at health.ny.gov<mailto: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<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<mailto:dhcp-users at lists.isc.org>>; bind-users at lists.isc.org<mailto: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<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<mailto: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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