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I have 3 computers on my local network, A B and C, all running Windows 7. They all have the same network configuration which uses my Netgear router for DNS. I am trying to access them via my Android tablet using ES File Explorer. I can access them all using their IP addresses. But I can only access B by name. This indicates a DNS problem. I don't have any problem mounting drives or using Remote Desktop or anything else from any one computer to any other using names, but I'm sure the problem has to do with my computers or router because I have two different brands of Android tablet and both behave in the same way. They did not have any prior settings which used the computer names A B or C so there is no way they could know the difference. I have tried adding the local IP's and computer names to the computers hosts files but nothing changed.

While trying to diagnose this I discover the following, which is probably worthy of a question all its own. If I run "nslookup A" it uses "Server: www.routerlogin.com" and returns an external IP address that I have never seen before. It seems to be owned by my ISP but is not the same as my static IP. If I run "nslookup B" I only get "Name: B." with a period on the end and no address line at all. If I run "nslookup C" I get the same unknown external address as before. If I run "nslookup A 8.8.8.8" to use Google's DNS I get "Non-existent domain". If I run "nslookup B 8.8.8.8" I get "Name: B." and no address just like when I use the local DNS. And finally when I run "nslookup C 8.8.8.8" I get "Non-existent domain" again.

So the computers which I cannot access by name, A and C, are behaving the same using nslookup, which is different from the computer which I can access, B. Not sure where to go from here.

Any help would be appreciated.

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  • what happens if you try to look up the A.local instead? While not dictated as a standard, many routers actually avoid using external resources for these kinds of lookups.
    – Jarmund
    Apr 8, 2015 at 9:00
  • What's the actual name of A B &C it self ? Apr 8, 2015 at 13:45

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Without knowing the actual name of B, this is mostly guesswork, but it seems to me that B shares the name of something somewhere that 8.8.8.8 has a DNS entry for.

Having said that, DNS Entries, where have you defined these? If you want your router to resolve these for you, your router needs to function like a proper DNS server, instead of just caching any entries it learns from the outside (which is what most routers do by default). This means that your router needs to

a) Know what to serve your android tablet, and everything else on your LAN, if queried about some of your hosts. I.e., create a small configuration pertaining to your network.

b) Know when to look at its own zone, rather than forwarding the query to an external DNS server. This is where the suffix .local comes in - It is often used as a method for keeping any DNS lookups internally. Basically, if your router is set up to utilize this, it will then identify B.local as something that it should have an entry for, and if not, return a result of a failed query, instead of pushing it further upstream.

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  • In particular assuming B is not literally B but is one "label" (no dot) it might match one of the hundreds of new TLDs approved by IANA in recent years, see iana.org/domains/root/db . These TLDs will have no addreseses of their own, only delegations to subdomains. Apr 8, 2015 at 12:42
  • @dave_thompson_085 that, in addition to the fact that a random DNS server in the chain of lookups might have B (still not literally, ofcourse) as one of its locally known hosts.
    – Jarmund
    Apr 8, 2015 at 12:50

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