Bypassing a wrong DNS entry

You are trying to connect to a remote machine via TCP/IP, you cannot ping the hostname but can ping the IP address. Your company is using a Domain Name Server (DNS), you suspect that there is a wrong DNS entry, you have no authority to modify this server (and it is also a Windows NT Server), you need to get to that machine but your applications only allows host names not IP addresses. What will you do next?

Easy. Run cfgtcp then option 10 to get to the host table entries, if the hostname and IP address already exists, add an alias (note that even if you have the correct entry here and your machine uses DNS, it will resolve the hostname / IP in DNS first, it will still find the wrong entry in DNS and resolve the hostname / IP incorrectly. To check if you are using DNS, run cfgtcp then option 13, Look at the Searched First field, *REMOTE means you are looking at DNS first, *LOCAL means you are using the host table entries (cfgtcp option 10), but do not change this setting to force searching for the host table entries first, this is a global setting, other applications might get affected). If it does not exit, add a new entry. Please note that this entry should be a hostname not existing in DNS, the purpose of this is not to change the Searched First setting, and the hostname to be resolved in DNS and not found so that it will force resolution in the host table entries allowing resolution on the "made up" hostname but with the correct remote IP address of the machine you are trying to "target".

Once the host table entry has been placed, you can configure your applications to use the "made up" host name until the DNS entry has been corrected.

This was first published in May 2001

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