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DNS confusion with internal domain and website

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  • DNS confusion with internal domain and website

    Im troubleshooting an issue with a fellow consultant. Company A has the domain of companya.com. They can access any website except www|d0t|companya|d0t|com which is externally hosted. When we add a www host record of the public ip of www|d0t|companya|d0t|com to the internal authoritative dns server, they are able to browse the website. I know for sure the host record isnt necessary. There arent any internel iis servers that would be causing some sort of internal redirection. Thoughts on why the host record is needed to browse that website?
    Last edited by phoeneous; 27th August 2009, 21:13.

  • #2
    Re: DNS confusion with internal domain and website

    The problem is that the internal domain name and the external domain name are the same (split-brain DNS). So when an internal user needs to connect to www.companya.com they will only look to the internal authorative DNS server. If they don't find an A or CNAME record for www then they won't be able to get to the web site. The internal DNS server knows that it is authorative for companya.com, it is never going to forward a DNS request for www.company.com to the external DNS server. It is going to return a DNS answer to the internal client of "name not found" or "no such name" or "record not found".

    The long and short of it is that you do need the internal A or CNAME record pointing to the external ip address.

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    • #3
      Re: DNS confusion with internal domain and website

      Originally posted by joeqwerty View Post
      The problem is that the internal domain name and the external domain name are the same (split-brain DNS). So when an internal user needs to connect to www.companya.com they will only look to the internal authorative DNS server. If they don't find an A or CNAME record for www then they won't be able to get to the web site. The internal DNS server knows that it is authorative for companya.com, it is never going to forward a DNS request for www.company.com to the external DNS server. It is going to return a DNS answer to the internal client of "name not found" or "no such name" or "record not found".

      The long and short of it is that you do need the internal A or CNAME record pointing to the external ip address.
      Thank you!

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      • #4
        Re: DNS confusion with internal domain and website

        Glad to help.

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