There is one technology normally associated with IP name resolution and that’s DNS (Domain Name System) or Smart DNS, this is probably because it’s the dominant system on the internet.  However in the average corporate network you’ll find all sorts of alternative methods to resolving names and IP addresses which have been around for years.  Here’s just a few of the common ones that you might come across:

Broadcasting: The use of mass broadcasts to help resolve names is of course very inefficient, basically a plea to the whole network asking for an answer.  You’d think that this method isn’t used any more and it’s true most network administrators have tried to remove it from their networks.   However for anyone who’s tried to troubleshoot a network of any size you’ll almost certainly find devices who routinely broadcast looking for name resolution.  A couple of reasons it doesn’t work well are it generates lots of unnecessary traffic and most routers won’t transmit the broadcasts anyway so calls are frequently just lost.  You can configure routers to pass on these message using the IP address helper function but this is not the way to run a fast efficient network.

Netbios over TCP/IP

Netbios was the primary method used by windows computers to resolve names and IP addresses, although again DNS is likely to have replaced it normally.  There are 4 methods to Netbios Name resolution and they are usually operated in a distinct order.

  • p-Node – Client contacts a WINS or NBNS server using unicast.  This needs to be configured on the client server to work properly but then just requires IP connectivity.
  • b-Node – Client attempts to  contact a WINS or NBNS server using a broadcast.  This will only be successful if there is a server on the same subnet or routers are configured to forward the request.
  • m- Node – Client uses b-node first then p-node is there is no reply to the initial broadcast.
  • h-Node – Client will first use a p-node unicast if configured and then fall back to a b-Node broadcast afterwards.

WINS

Windows Internet Names Service is a Microsoft implementation of the NetBios (NBNS) protocol.  It’s a dynamic and distributed method of name resolution used mainly in Windows environments.  It has all name resolutions saved on central WINs servers, and indeed in some implementations the WINS service was installed automatically on Microsoft Windows server installations. Again it works best when the WINS server is configured correctly on the client, otherwise it will fall back on broadcasts like NBNS.

LMHOST

This is a simple static file similar to a hosts file which is must be created, distributed and kept updated by the network administrator.  If a client is configured in h-node then the LMhosts file will be consulted as a fall back method.  It can create a lot of work and potential issues in large dynamic environments although it can be used to distribute names of key servers which are unlikley to be moved or modified.

Read More

3 Comments Networking, News

3 thoughts on “IP Name Resolution”

  1. Thanks for this, would the client use the hosts file to resolve an address too? If so which order would it come i.e. would I be able to stop name resolution if I added a specific address to the hosts file on windows machine? Thanks !!!

    1. Yes it would check for any entry in the hosts files. Basically first machine checks resolver cache, then hosts file, then DNS request followed by the Netbios resolutions listed here. So if you put a name and IP address in the hosts file, there would be no Netbios or DNS request sent.

Leave a Reply

Your email address will not be published. Required fields are marked *