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I have two DNS servers in my office, Gob and Tobias. They are both running Ubuntu and BIND. Their BIND config files are identical. We've been using Gob for the last month or so. When we switched to Tobias for the first time today, everything kept working fine except we were no longer able to print. Switching back to Gob fixed the problem.

Any idea as to why changing DNS servers, which doesn't seem to me to have all that much to do with printing, could make it so people can't print anymore?

Edit: After some more testing, it's unclear whether only Gob works, only Tobias works, it works sometimes under either, or if the printing problem is even related to the DNS server switch at all. Pretty cool.

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+1 for Gobias Industries. –  phoebus Oct 18 '10 at 20:11
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How are your printers shared on the network? –  Steven Monday Oct 18 '10 at 20:18
    
I don't know enough about printers to answer that question. If it makes sense to list the possibilities, maybe I could answer. –  Jason Swett Oct 18 '10 at 20:21
    
is the printer plugged directly into a computer via USB acting as your print server, or is the printer networked. Is there a PC with a shared printer that jobs to a networked printer? How do your local pc's reference the printer? –  Matt Oct 19 '10 at 3:35
    
Are the printers getting their IPs from DHCP or are they set statically? –  Christopher Oct 20 '10 at 20:19

5 Answers 5

A couple of things:

  1. Are clients configured to use Tobias as well as GOB for DNS name resolution?

  2. What is the TTL on the DNS record for the printer and did you wait for the TTL to expire or flush the DNS cache on the client before trying to print?

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1. No, this is being done through the router. 2. I don't know, and how would I flush the DNS cache on the printer? –  Jason Swett Oct 18 '10 at 20:09
    
1. How does DNS work exactly in your environment if the clients are using the router for DNS instead of Gob and Tobias? Does the router driect requests for your internal DNS zones to Gob and Tobia then? If so, is the router configured to direct requests to Tobias? Also, the printer shouldn't need to resolve DNS names in order for users to print to it, so the printers DNS configuration should be largely irrelevant. –  joeqwerty Oct 18 '10 at 20:18
    
Sorry, I explained that badly. The router is telling all clients to use Tobias as the DNS server. And yeah, I wouldn't think the DNS servers would have anything to do with printing. –  Jason Swett Oct 18 '10 at 20:24
    
Let me clarify: The printer itself doesn't need to perform DNS lookups to resolve DNS names in order for the printer to function correctly, so whether or not the printer is configured to use Gob and\or Tobias is largely irrelevant to the problem. Where DNS does come in to play regarding the printer is here: if your clients print to the printer by name (instead of ip address) then the clients need to be able to resolve the DNS name of the printer. Consequently this means that both Gob and Tobias need to have the same DNS record for the printer that resolves to the same ip address. –  joeqwerty Oct 18 '10 at 20:29
    
Well, neither Gob nor Tobias have any entries that have anything to do with the printer. –  Jason Swett Oct 18 '10 at 20:34

When you switched to using Tobias did you check on the print server that the printer can resolve?

You don't happen to have everything DHCP do you? Often servers are set static. Check you've actually changed all DNS to point to Tobias.

Restart all the LAN machines so their DHCP leases are renewed.

Or do a

ipconfig /release ipconfig /renew

on the windows cmd line.

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I didn't check on the print server that the printer can resolve. How do I do that? I do have everything on DHCP. –  Jason Swett Oct 18 '10 at 20:08
    
The printer shouldn't need to resolve DNS names in order for users to print to it, so the printers DNS configuration should be largely irrelevant. –  joeqwerty Oct 18 '10 at 20:17
    
That's what I thought! –  Jason Swett Oct 18 '10 at 20:22
    
@joeqwerty - depends how the printer is connected! A shared print queue might exist on a machine dedicated as a print server (which Jason sees on his network as the printer), but the printer itself can be networked like lpr etc. If the queue is set up to print to a named address and it can't resolve then that'd explain it. –  Matt Oct 19 '10 at 3:30

You didn't tell very much about the printers. There at least 2 possibilities here:

  1. People (their computers) not seeing the printers because they don't resolve anymore. Unlikely, because you said the DNS server where identical.

  2. Some printers require a DNS server to work (why ever, I#ve seen this with some HP and I also believe with some Canon printers. If the printers had only one server configured, and you took it offline, then someone has to tell the printers where the new DNS server is.

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My first guess would be the configuration actually isn't identical, for whatever reason. Tobias is probably not resolving the printer, for whatever reason, and so clients can no longer find it. You can very easily check this:

C:> nslookup <hostname of printer>  <ip of gob>
C:> nslookup <hostname of printer>  <ip of tobias>

If they don't return the same thing, well, take a REALLY good look at the zone files, and check for /etc/hosts entries.

The "sometimes" symptoms also make me think this is an issue, since it could be caused by cached DNS records, some clients using the IP rather than hostname, and/or some clients still using Gob as their nameserver.

If both lookups return the same thing, it's likely a problem with the printer itself. Check network configs on the printer, as maybe it is dependent on DNS as others have suggested.

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up vote 0 down vote accepted

The problem has gone away by itself, meaning all these answers are probably irrelevant. Sorry about that.

Since Stack Overflow's interface forces me to keep my "accept rate" up or else people will whine about it, I'm putting this "answer" here so I can select it in a couple days.

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