Slow internet resulting from DNS settings?

Zoomer

Our internet has been slow at our office. I've been trying to figure out why. I asked for some help and one of the other guys changed the DNS settings on the local computers to an outside DNS server. (219.109.x.x) We were using an internal DNS (10.0.2.x).

All of a sudden, everyone's internet starting working faster. I'm glad he fixed it. I had been working on it forever and couldn't figure it out. Now, is there any downside to doing that? Security issues? Or is that fine?

sprkymrk

I wouldn't like that for a solution, though it's a good clue as to what to look at to fix the problem.

Make sure your internal DNS is working correctly with forwarders or whatever. Do you have security in place that performs a reverse lookup on all requests before allowing them? I had this one time an every request that didn't have a PTR record took like 30 seconds to time out before the query would work. Check your firewall too.

JDMurray

For an external DNS source other than your ISP, the OpenDNS servers (208.67.222.222 and 208.67.220.220) are fast and reliable (that is, not poisoned with phishing and Malware sites).

Zoomer

It was some old ISP DNS servers that they used to use. So I would have to worry about phishing and malware? Is there any other security issues I should worry about?

JDMurray

Untrusted DNS servers are the big worry. If you use internal DNS servers, make sure they only perform zone transfers with known, authenticated servers. You don't want malicious Web sites in your DNS records, or the map of your intranet transfered to a malicious server.

DNS security issues

DNS cache poisoning

Tyrant1919

They covered what I would assume would be causing the slowness.