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Will there be trouble if non-server machines:
1. don't have forward addresses that match in-addr.arpa?
2. don't have forward addresses?
3. don't have in-addr.arpa PTRs?

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6 Answers 6

up vote 4 down vote accepted

You may not run into trouble, but it really is worth the fairly minimal effort to set it all up.

$GENERATE is your friend.

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Note that $GENERATE is a BIND function. If you're using something else (like Windows DNS), well, it's usually just as simple but a bit different. –  Mark Henderson Aug 11 '11 at 21:59
    
in windows, when you create the forward record there's a checkbox to create the reverse automatically –  Sirex Aug 12 '11 at 10:18
    
I was trying to justify not doing it because I was feeling lazy, but this is better. –  84104 Aug 12 '11 at 15:39

No there is no problem with that setup. If your machine connects to other machines it makes you "suspicious" but not more.

If the IP is used for outbound emails you will see a lot of trouble as not having a valid reverse DNS makes you look like a Spammer or Spambot. Or at least as an incompetent postmaster.

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Non-server machines don't need PTR records at all, although if you happen to maintain an internally visible reverse DNS map for your own use that wouldn't hurt.

Making your desktop machines' names visible to the outside world might be considered a security risk, although it also falls squarely into the "security by obscurity" argument. That said, if you name your workstations after the employee that uses them then that information could be used for social engineering.

For IPv6 the IETF consensus appears to be that it's simply not worth the effort, particularly when using SLAAC which causes non-servers to pick random addresses and change them every so often.

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  1. Possibly, depending on the scenario.

  2. Most likely

  3. Not likely

There are very few cases where a PTR record is actually useful (such as for an outbound email server) but even then it' not a standardized requirement.

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Trouble? Not really.

But it will be a PITA in the long run when web servers or terminal servers can't map IPs to workstation names to put them in log files...

It all depends how many computers you have in the network, if only a few then you can easily memorize their IP addresses and those dozen DHCP IP addresses.

Also, lack of rDNS zone will make SSH login longer unless you configure sshd to not perform reverse lookups.

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I've never seen a problem with client/server, client/client, or server/server communication due to the lack of a rDNS zone. How do you propose that the lack of such will cause problems for web servers or terminal servers resolving workstation names from their ip addresses? Why would a web server or Terminal Server need to resolve a workstation name from it's ip address? What purpose or function would that serve or facilitate? Furthermore, a rDNS zone is not required in a Windows based domain so how is it that the various Windows OS's and roles function without a rDNS zone? –  joeqwerty Aug 11 '11 at 22:12

Avoid it like the plague on a LAN.

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6  
Wanna justify that answer with some more detail or shall I just downvote it as subjective? –  Tom O'Connor Aug 11 '11 at 22:38

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