Can’t access SOME websites – DNS related issue

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    nomade0
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    #156056

    Hi everyone!

    I’m on a domain network run by a SBS 2008 server, and with 3-4 clients running Win 7 Pro 32 bits.

    As part of my job I’m working on 2 websites, which I access via FTP quite often. Since a week or two, I can’t seem to be able to access these websites anymore. I thought they had a problem, but then I realized I can ping them, connect to them via a proxy, or simply from my home.

    From any computer on the work domain, they are not accessible. From any other computer, they seem accessible. Yesterday, I was even unable to connect via FTP to one of them (didn’t try the other one), which never happened before. Though today I have FTP access again.

    Leaving the FTP anomaly aside for now, I worked around the problem by changing the DNS on my work station from 192.168.1.100 (the SBS 2008 server) to an OpenDNS address. It solved everything, so I pretty much know it’s DNS related.

    But I want to be able to keep using my 2008 server as DNS server. What’s going wrong? I don’t have much clue as to how to troubleshoot this.

    I tried already:

    • ipconfig /flushdns on my work station and on the server.
    • Using different browsers and different computers on the domain

    I suspect/think:

    • I suspect a DNS caching issue (since it happens ONLY on 2 websites I visit very frequently to work on, (though it doesn’t happen on Google Apps which I use even more often)). Hence the /flushdns, but nothing changed.
    • I suspected the router, but since changing the DNS on a client machine solves the pb, it doesn’t make sense.
    • I read about MTU… but again, different DNS = no problem, so that shouldn’t be it.
    • There is no firewall/antivirus on the SBS 2008 (fresh install), so that’s not an issue.

    I would appreciate any help or suggestion… Thanks a lot!!

    Olivier

    Here is the result of an ipconfig /all from my work station:

    Code:
    Windows IP Configuration

    Host Name . . . . . . . . . . . . : COMPANYNAME-3
    Primary Dns Suffix . . . . . . . : companyname.local
    Node Type . . . . . . . . . . . . : Hybrid
    IP Routing Enabled. . . . . . . . : No
    WINS Proxy Enabled. . . . . . . . : No
    DNS Suffix Search List. . . . . . : companyname.local

    Ethernet adapter Local Area Connection:

    Connection-specific DNS Suffix . : companyname.local
    Description . . . . . . . . . . . : Intel(R) PRO/100 VE Network Connection
    Physical Address. . . . . . . . . : 00-12-3F-BB-01-77
    DHCP Enabled. . . . . . . . . . . : Yes
    Autoconfiguration Enabled . . . . : Yes
    Link-local IPv6 Address . . . . . : fe80::5c4f:e3ac:136e:911d%10(Preferred)
    IPv4 Address. . . . . . . . . . . : 192.168.1.112(Preferred)
    Subnet Mask . . . . . . . . . . . : 255.255.255.0
    Lease Obtained. . . . . . . . . . : Thursday, September 01, 2011 9:15:01 AM
    Lease Expires . . . . . . . . . . : Friday, September 09, 2011 10:34:04 AM
    Default Gateway . . . . . . . . . : 192.168.1.254
    DHCP Server . . . . . . . . . . . : 192.168.1.100
    DHCPv6 IAID . . . . . . . . . . . : 234885695
    DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-BC-39-94-00-12-3F-BB-01-77
    DNS Servers . . . . . . . . . . . : 192.168.1.100
    NetBIOS over Tcpip. . . . . . . . : Enabled

    Tunnel adapter Local Area Connection* 11:

    Media State . . . . . . . . . . . : Media disconnected
    Connection-specific DNS Suffix . :
    Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
    Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
    DHCP Enabled. . . . . . . . . . . : No
    Autoconfiguration Enabled . . . . : Yes

    Tunnel adapter isatap.companyname.local:

    Media State . . . . . . . . . . . : Media disconnected
    Connection-specific DNS Suffix . :
    Description . . . . . . . . . . . : Microsoft ISATAP Adapter #2
    Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
    DHCP Enabled. . . . . . . . . . . : No
    Autoconfiguration Enabled . . . . : Yes

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