Manually provided DNS server addresses are higher priority than DHCP's

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With the recent revelation of DNS server security issues, many have expressed a desire to use DNS servers they know to be secure rather than the servers specified by their routers via DHCP, which often are those of a particular ISP.
When you manually enter a DNS server address in Mac OS X Leopard's Network preference pane, the manually entered address(es) appear below any DHCP-provided addresses (which are shown in grey as they are unchangeable), leading one to assume that DHCP-provided addresses always have priority over any a user may specify.
However, a check of the /etc/resolv.conf file generated by Mac OS X shows that in fact user-provided DNS addresses will supercede any provided by DHCP.
As an example, if your router promotes itself as a DHCP server, its IP address, say "192.168.0.253," will appear, greyed out, in the Network->Advanced->DNS preferences pane.
If you then add, say, OpenDNS' addresses of "208.67.222.222" and "208.67.220.220," the preferences window will show:
192.168.0.253 (greyed out)
208.67.222.222
208.67.220.220
But the generated /etc/resolv.conf will show the order Mac OS X will actually reference the servers is:
nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 192.168.0.253
While this is non-intuitive, given how the addresses are displayed in the preference pane, it is exactly the way a user would hope things would work - allowing one to specify DNS servers to be used in lieu of any a router provides, especially handy if the router propagates the address of a DNS server that is having issues, that is untrusted or is simply overloaded or offline.
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That's very good to KNOW.
I figured it as such as I have some manual entries for the office and I don't use profiles, so it stays there when I go home.
I notice a slow-down when office DNS entries are used at home -as one would suspect.
I do like KNOWING that it's the case though - thanks for the info!
Scott

Similar Messages

  • Re: Manually provided DNS server addresses are higher priority than DHCP's

    This tip may be published at the mods' leisure.

    That's very good to KNOW.
    I figured it as such as I have some manual entries for the office and I don't use profiles, so it stays there when I go home.
    I notice a slow-down when office DNS entries are used at home -as one would suspect.
    I do like KNOWING that it's the case though - thanks for the info!
    Scott

  • FYI: Manually provided DNS addresses are higher priority than DHCP's

    As an FYI to folks here concerned about the issue, manually entered DNS addresses do indeed supercede any provided by DHCP despite what you might be led to believe by the appearance of the Network->Advanced->DNS preference pane.
    When you manually enter a DNS server address in Mac OS X Leopard's Network preference pane, the manually entered address(es) appear below any DHCP-provided addresses (which are shown in grey as they are unchangeable), leading one to assume that DHCP-provided addresses always have priority over any a user may specify.
    However, a check of the /etc/resolv.conf file generated by Mac OS X shows that in fact user-provided DNS addresses will supercede any provided by DHCP.
    As an example, if your router promotes itself as a DHCP server, its IP address, say "192.168.0.253," will appear, greyed out, in the Network->Advanced->DNS preferences pane.
    If you then add, say, OpenDNS' addresses of "208.67.222.222" and "208.67.220.220," the preferences window will show:
    192.168.0.253 (greyed out)
    208.67.222.222
    208.67.220.220
    But the generated /etc/resolv.conf will show the order Mac OS X will actually reference the servers is:
    nameserver 208.67.222.222
    nameserver 208.67.220.220
    nameserver 192.168.0.253
    While this is non-intuitive with respect to how the addresses are displayed in the preference pane, it is exactly the way one would hope things would work - allowing you to specify DNS servers to be used in lieu of any a router provides, especially handy if the router propagates the address of a DNS server that is having issues or is simply overloaded or offline.
    Note that as I do not have an unpatched copy of Leopard available, I cannot say if this has always been Mac OS X's behavior or if this ordering was added by Security Update 2008-005.
    Regardless, this also means no special modifications are required to try to "turn off" the honoring of DHCP-provided DNS server addresses.

    Topher Kessler wrote:
    That's good to know. However, users may wish to solely provide their own DNS servers and not have the chance that in case their DNS servers are unreachable they end up using the default one.
    that's the problem. there is no way to easily remove the default DHCP provided DNS server. there is [a hack|http://www.macosxhints.com/article.php?story=20080725172011439&query=dns] that has been discussed in several threads but it can break various functions.
    I guess one option would be to just add more custom DNS servers to ensure they get used over the default one.
    That's the only reasonable thing to do.

  • Can't delete grayed-out DNS server addresses

    I want to replace two grayed-out DNS server addresses from the Network panel (under the DNS tab in "Advanced…"), to replace them with OpenDNS settings. But they can't be selected/deleted. How do I get around this problem?

    That is correct - those are provided by your router and can not be deleted - you can add Open DNS servers (click the + sign) or log into the router admin page (I recommend this way) and have your router use the Open DNS servers fro everything on your network (this will change the grayed out ones)
    LN

  • How to prevent changing DNS server address

    I work for a public school district. We just purchased our first batch of Win 8.1 PCs, but they are not the Pro version, so there is no gpedit.  I want to prevent students from accessing the TCP/IPv4 Properties dialog box in order to ensure that the
    DNS server address is always obtained automatically.  Can anyone tell me how to do this using regedit, or any other way?  Thanks!

    Easiest way is to assign these students a standard user account (without admin rights).. They cant change any system setting then.. Other than restricting privileges I don't think you have option here since you don't have group policy editor ..
    There could be a possibility to do this using regedit But it is not recommended since there are no any official article for this other than below untested third party article form ehow
    http://www.ehow.com/how_8110801_disable-tcpip-properties-regedit.html
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  • Passing DNS server addresses through DHCP?

    I'm setting up NAT & DHCP (both as a DHCP client & DHCP server) on a 2621. Since the DNS server address(es) are received on the router's interface configured as a DHCP client, is there a way to pass these (possibly dynamic) address(es) on the internal network clients? What I see in the DHCP server functionality is that the option specifying what DNS server(s) are passed on to clients is hard coded. If hard coding the option is my only choice, do I have any guarantee that the ISP will always use the same IP address(es) for its DNS servers?
    Any insight would be appreciated.

    Thats exactly what the 'import all' command is for.
    In your DHCP server, if you supply the command 'import all', it will seek the DHCP information that was given to it on the interface that has "ip address dhcp". It will store the information like DNS into your DHCP server, and then send that out to all devices receiving DHCP addresses from your server.

  • Detect "Obtain DNS server address automatically" set

    Can anyone help me with a minor issue?
    I am trying to detect if this setting is set to manual or automatic
    I am currently using this code
    Get-WmiObject -Class Win32_NetworkAdapterConfiguration -Filter "IPEnabled=TRUE" | Select PSComputerName,DNSServerSearchOrder
    The problem is it returns the servers and not the actual setting of automatic vs manual.
    Powershell v2

    Hi JustuslV,
    Optionally, you can retrieve or set a value corresponding to "Obtain DNS server address automatically" by using the two registry entries, DhcpNameServer and NameServer, which you can find at the following registry location:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces
    \{AdapterIdentifier}
    If the value of NameServer is null, the client tries to obtain a DNS server address automatically from the DHCP server.
    Refer to:
    Part 5: Scripting DNS on Clients
    And you can refer to this script to get the related registry value:
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    $path='HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces'
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    Best Regards,
    Anna Wang

  • "Back to my Mac isn't working properly because your DNS server isn't responding. Contact your ISP for an alternate DNS server address, and enter it in Network Preferences".

    Hi, i am trying to setup back to my mac at home but I get the error "Back to my Mac isn't working properly because your DNS server isn't responding. Contact your ISP for an alternate DNS server address, and enter it in Network Preferences".
    There is no documentation on how to solve this anywhere.
    I have an Arris router set to bridged mode which is connected to a 5th generation airport extreme. I have tried using the google dns servers instead of the one assigned by the cable company in the AE but I still get the same error.
    Any help would be much appreciated
    Kenneth

    New to BTMM, I got stung today with the silly DNS problem message. Solution:
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    dscacheutil -flushcache;sudo killall -HUP mDNSResponder
    2)System preferences > iCloud > untick BTMM then tick it again. The warning should have disappeared.
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    But this will be a problem for my ipad and iphone that uses wifi.
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    On the initial set up of the air port extreme the dns server numbers are black, how can i make them grey?

    Black would indicate that the AirPort Extreme is set up as the main router. Is this what you want?
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  • Give LAN higher priority than wireless / deactivate wireless if LAN is connected

    Hi.
    What I want to do is quite simple: Im my office there is a quite fast LAN connection and a rather poor wireless connection. Therefore, I want to tell my device: "If there is a LAN cable plugged in, just use LAN. Do not use Wifi in this case. If there is no LAN cable plugged in, try to connect to Wifi."
    It is really annoying to change that manually each time.
    I have already changed the network connection priority in Windows 7 as described here: http://support.microsoft.com/kb/2526067
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    Wifi Device: Intel Centrino Wireless-N 2230
    Driver Date 30.09.2012
    Driver Version 15.3.1.2
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    Hi cis,
    do you by any chance have Access Connections installed on your system?  It is possible that the WLAN adapter is set to a higher priority than LAN in your location profile which is causing the behaviour.  If you don't have AC installed it may be a possible solution you could try. 
    Link to another thread on this subject;
    http://forums.lenovo.com/t5/ThinkVantage-Technologies/Access-Connections-disable-WiFi-on-Wired-Conne...
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