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How is it possible to ping a computer name and get reply if not in DNS

Posted on 2014-07-25
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Last Modified: 2014-09-16
I have been assigned an existing project that consists of two domains (Domain A and Domain B) on the same physical network. These two domains do not hat trust relationships and each domain has their own domain controllers and DNS servers, but share a common DHCP server and default gateway.

Domain A was the first domain and Domain B was added later to facilitate a company division that is preparing to separate into a new, independent company.

Some computers on Domain A needed to be accessed by computers on Domain B so the prior admin added a DNS zone to the DNS server in Domain B that listed computer host names and IP addresses from Domain A.

There are no WINS servers running or being referenced on the Domain B domain controller

From the domain controller in Domain B, I can ping the computers listed in that DNS zone by computer name and get a reply, as expected.

However, I can also ping computers in Domain A that are not specifically listed in that DNS zone in Domain B, which makes me think that there must be a link I am missing.

The DNS server in Domain B does not have any forwarders and is just using Root Hints.

I have examined the domain controller in Domain B and it does not have any entries in the local hosts or LMHosts files in the c:\windows\system32\drivers\etc folder

How is it possible that I can ping a non-public computer by name that is not specifically listed in a DNS zone, Host file, LMHosts file or via a forwarder to a Domain A DNS?

Thanks,

Dave
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Question by:dcadler
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Expert Comment

by:Rob Williams
ID: 40219358
NetBIOS and DNS use multiple methods to resolve names such as those you mentioned LMhost, Hosts, DNS, WINS but also simple name caching.  I forget the order, and it varies based on node type,  but when one fails it tries another.  However you cannot count on caching for reliability.
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Expert Comment

by:John Hurst
ID: 40219368
Given your conditions, you are better off to access a computer in the other domain. I do that reliably whenever I cannot resolve a name by DNS.
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Accepted Solution

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Rob Williams earned 500 total points
ID: 40219374
PS-  The following is a good article for a type H (Hybrid) node, the most common, name search order:
http://networkadminkb.com/KB/a118/understanding-dns-client-service-how-name-resolution-works.aspx
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Expert Comment

by:DrDave242
ID: 40220081
It could be a simple NetBIOS broadcast that's resolving that name, since they're all on the same network. Are you pinging just the hostname or the fully qualified domain name?
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