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Typed "ipconfig /all" and see 2 different DNS.......

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  • Typed "ipconfig /all" and see 2 different DNS.......

    I had typed “ipconfig /all” and I can see as above -
    "DNS Suffix Search list" - 2 different DNS address (abc.msft, sweethome.west.com)

    In Ethernet adapter Local area Connection 2:

    Connection-specific DNS Suffix: sweethome.west.com
    Description: my wireless USB Network Adapter #2
    DNS Servers: 192.168.1.1
    192.168.1.1 (2 DNS servers IP address)

    “DHCP Server” and “Default Gateway” IP address I can see just one.

    Now question is why is it showing me like this?

    1. abc.msft is running on sweethome.west.com ???
    2. It is 2 different and separately running (“abc.msft” & “sweethome.west.com”)??
    3. Is it possible using abc.msft or sweethome.west.com can go in each other's computer??
    4. I would like to know role of / importance of / about DNS Cached lookups (I have folder “.” under this Cached lookups) (“abc.msft” is my DNS server)

    Anyone please explain me!!

    Note: This is a home computer /test server computer.

  • #2
    Re: Typed "ipconfig /all" and see 2 different DNS.......

    im not sure what your asking, but the connection specific DNS suffix is how you resolve names on your network specific to that adapter. it is assigned via DHCP generally... is that what your asking?
    http://www.microsoft.com/technet/pro....mspx?mfr=true

    there can only be one DHCP server on a network, thus the single address.

    you can only have one default gateway as well.. again, 1 address.

    and your asking if people can use these DNS entries to gain access to your computer? well, if you have no A record on a public DNS, then i guess no... if you have a NAT in place for the machines and the ports are wide open, then i suppose someone could find you if they had your IP...

    the cached entries are to make lookups faster... this information will not be replicated with other DNS server. the only entries replicated are the AD integrated objects..

    does that explain anything or am i way off on what youre asking?
    Last edited by James Haynes; 20th August 2007, 14:58.
    its easier to beg forgiveness than ask permission.
    Give karma where karma is due...

    Comment


    • #3
      Re: Typed "ipconfig /all" and see 2 different DNS.......

      Originally posted by James Haynes View Post
      there can only be one DHCP server on a network
      Um..., not so. It's advisable to have 2 DHCP servers when you want redundancy, just make sure they don't overlap.


      Originally posted by James Haynes View Post
      you can only have one default gateway
      True.
      Best wishes,
      PaulH.
      MCP:Server 2003; MCITP:Server 2008; MCTS: SBS2008

      Comment


      • #4
        Re: Typed "ipconfig /all" and see 2 different DNS.......

        It would be a lot easier to provide help if you included the output from your IPCONFIG / ALL and described how your wired and wireless NICs were hooked up.

        Having 2 DNS's is not unusual. I'm taking DNS, etc. from my ISP right now as held in my router:

        Code:
        Windows IP Configuration
        
                Host Name . . . . . . . . . . . . : ---
                Primary Dns Suffix  . . . . . . . :
                Node Type . . . . . . . . . . . . : Broadcast
                IP Routing Enabled. . . . . . . . : No
                WINS Proxy Enabled. . . . . . . . : No
        
        Ethernet adapter ---:
        
                Connection-specific DNS Suffix  . :
                Description . . . . . . . . . . . : ---
                Physical Address. . . . . . . . . : ---
                Dhcp Enabled. . . . . . . . . . . : Yes
                Autoconfiguration Enabled . . . . : Yes
                IP Address. . . . . . . . . . . . : 192.168.1.104
                Subnet Mask . . . . . . . . . . . : 255.255.255.0
                Default Gateway . . . . . . . . . : 192.168.1.254
                DHCP Server . . . . . . . . . . . : 192.168.1.254
                DNS Servers . . . . . . . . . . . : 192.168.1.254
                Lease Obtained. . . . . . . . . . : Monday, August 20, 2007 7:13:49 PM
                Lease Expires . . . . . . . . . . : Tuesday, August 21, 2007 7:13:49 AM
        But on my router:

        Code:
        Primary DNS:  1.253.128.34
        Secondary DNS:  1.253.128.11
        In the past, I had the ISP punch 2 DNS addresses through to the local NIC.

        NSLOOKUP will try the first DNS and, if it fails, use the second. MS allows more than 2 on its "Advanced" tab.

        You can by definition only have 1 gateway per NIC.

        I agree w/ Paul on DHCP. Depending on use (SOHO), 1 DHCP may be enough.
        Last edited by rvalstar; 20th August 2007, 22:04.
        Cheers,

        Rick

        ** Remember to give credit where credit is due and leave reputation points sigpic where appropriate **

        © 2006-2099 R Valstar. This post is offered "as is" for discussion purposes only with no express or implied warranty of any kind including, but not limited to, correctness or fitness for use. Nothing herein shall be construed as advice. Attempting any activity based on information in this post is done at your own risk.

        Comment


        • #5
          Re: Typed "ipconfig /all" and see 2 different DNS.......

          Originally posted by PaulH View Post
          Um..., not so. It's advisable to have 2 DHCP servers when you want redundancy, just make sure they don't overlap.
          fair enough... i guess what i was getting at there is usually only 1 active DHCP server PER SCOPE online at a time. overlaping will cause some problems. sorry for any confusion. but you will never see an 'ipconfig/all' with two DHCP addresses like this:
          Code:
          IP Address. . . . . . . . . . . . . : 192.168.5.44
          Subnet Mask . . . . . . . . . . . : 255.255.255.0
          Default Gateway . . . . . . . . : 192.168.5.1
          DHCP Server . . . . . . . . . . . : 192.168.5.25
                                               192.168.5.69
          DNS Servers . . . . . . . . . . .  : 192.168.5.10
                                                        192.168.5.78
          Primary WINS Server . . . . . : 192.168.5.10
          (i cant get them to line up right cause it chops off the blank spot at the front )

          thanks for catching that and making the appropriate correction.
          Last edited by James Haynes; 20th August 2007, 21:46.
          its easier to beg forgiveness than ask permission.
          Give karma where karma is due...

          Comment


          • #6
            Re: Typed "ipconfig /all" and see 2 different DNS.......

            Please correct me if I'm wrong here, but something Rick said has prompted me to try this out on you:

            When there are 2 DNS servers specified (often the case), I believe it is a common misconception that if the first one doesn't provide the lookup requested even though it is working, the second one is subsequently asked to provide the name lookup. This is not true. What happens is that if the first one FAILS COMPLETELY to provide any response at all, the second one is asked for the lookup. I think this is what Rick is referring to, but I wanted to clarify. Elsewhere in this forum I have seen a recommendation to put only the IP of the domain controller in as the DNS, but I beg to differ. If the IP of the router is specified as the second DNS, the client computers can still browse the web if the domain controller goes down. This is because it will have failed completely to provide any response, and so the second DNS server (i.e the router) will respond and allow browsing from the clients.

            I have a client who relies on offline files to bring his server down and the clients don’t even notice, except they got kicked off the web. Then I told him to put the router’s IP as secondary DNS and then the client machines don’t notice at all when he brings his server down. (I dunno why he does it so often – maybe he takes it home to give it a polish or something.)

            Back to the case in point, it is a bit overkill to have 2 DHCP servers in a small network, and indeed James is correct in saying that the IPCONFIG /ALL command will never result in 2 DHCP servers (because the PC only broadcasts its request and receives a reply from one DHCP server, and goes with that one).

            Also, you won't get 2 gateways either, and I do not yet know why MS allow you to put multiple gateways in but I'll look into that and find out. I have tried to put 2 gateways in and it has no effect at all – the 2 gateways I put in were 2 routers on different ADSL lines but all connected on the same subnet, so I turned off gateway number 1 expecting the clients to switch over to using gateway number 2 but they didn’t do that, so I remain puzzled about that one.
            Best wishes,
            PaulH.
            MCP:Server 2003; MCITP:Server 2008; MCTS: SBS2008

            Comment


            • #7
              Re: Typed "ipconfig /all" and see 2 different DNS.......

              That is what I meant re: "fails". Should have been more specific.

              Interesting re: more than one gateway:

              http://www.microsoft.com/technet/com...g0903.mspx#E3F

              Dead Gateway Detection
              When there are multiple default gateways configured on an interface, the TCP component of Windows TCP/IP uses dead gateway detection to detect the failure of the default gateway and to adjust the IP routing table to use the next default gateway in the list. A host might be configured with multiple default gateways when the subnet on which it is located has multiple routers for fault tolerance of routed traffic. If the first router in the configured list becomes unavailable, TCP eventually updates the IP routing table to use the next default gateway in the list.

              When a TCP segment for a TCP connection forwarded via the default gateway is retransmitted three times (by default), dead gateway detection changes the Route Cache Entry (RCE) for that remote IP address to use the next default gateway in the list as its next-hop address. An RCE is an entry in the route cache, which stores the next-hop IP address for a destination address.

              When one fourth of the TCP connections routed through the default gateway have had their RCEs adjusted to the next default gateway, dead gateway detection informs IP to change the computer’s default gateway to the one that the adjusted connections are now using. If TCP connections continue to fail, dead gateway detection attempts to use the next default gateway in the list, eventually returning to the first configured default gateway after cycling through the entire list.

              Dead gateway detection monitors only TCP traffic. If connectivity fails for other types of traffic, the default gateway is not switched. Dead gateway detection can cause the default gateway configuration to change when a remote router fails. Remote routers in the path between the host and the destination that fail might also cause TCP connections forwarded along that path to fail and for the host to switch its default gateway. Because dead gateway detection relies on an end-to-end protocol (such as TCP), a host can switch its default gateway even when the current default gateway is fully operational.
              Cheers,

              Rick

              ** Remember to give credit where credit is due and leave reputation points sigpic where appropriate **

              © 2006-2099 R Valstar. This post is offered "as is" for discussion purposes only with no express or implied warranty of any kind including, but not limited to, correctness or fitness for use. Nothing herein shall be construed as advice. Attempting any activity based on information in this post is done at your own risk.

              Comment


              • #8
                Re: Typed "ipconfig /all" and see 2 different DNS.......

                That's interesting indeed. My "two routers" experiment should have worked, according to that article. I need to revisit the experiment and work it out.

                Thanks for posting it.
                Best wishes,
                PaulH.
                MCP:Server 2003; MCITP:Server 2008; MCTS: SBS2008

                Comment

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