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OS X (latest version of High Sierra) is doing something strange when I try to connect to my campus wireless network.

On a regular basis, it is adding an incorrect DNS server (10.0.0.255) "on top" of the list of DNS servers that actually is appropriate for my campus network. I have to go in and manually delete the incorrect server, which appears by itself; when I do so, the full correct list shows up and everything returns to normal.

How do I prevent OS X from doing this automatically?

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Firstly, I'm going to assume that your wireless IP address is provided by DHCP (Domain Host Configuration Protocol), in addition to DNS settings from the same DHCP server.

It’s not clear how 10.0.0.255 is not a valid and correct DNS as opposed to the DNS handling many requests and responding slowly.

If the DNS of 10.0.0.255 really does not work, you may want to check with the campus wireless providers. For all you know; you could be connecting to someone pretending to be the campus wireless; and also failed to setup their fake AP correctly.

You could also just manually enter the one correct DNS in your settings which will remove the second response and wait until the network gets fixed.

  • Thanks @bmike... I'm going to add a very minor edit ... It reads much better – Grunkle Stan Aug 29 '18 at 3:49
  • I have checked with IT. The added server is not valid on our network—I can’t connect to anything while it’s active. (The IT group also provided the list that I’m currently using.) The correct list is there but it’s invisible until I delete the incorrect address. I’m trying to understand what’s causing DHCP to do this and if there’s a way to prevent it. – aeismail Aug 29 '18 at 3:53
  • @Aeismail Now it sounds like you have some prefered DNS server already setup. exactly like this guy... superuser.com/questions/1317504/… I'm not condoning a complete reset of all your settings... but you may want to look at mandarapte.com/apple/… – Grunkle Stan Aug 29 '18 at 4:08
  • Edit away - that's how we do it : - ) Thanks for answering – bmike Aug 29 '18 at 4:09

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