name resolution on a LAN

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fran1942

82 posts

Master Geek

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#156075 18-Nov-2014 17:42

Hello, just a bit confused on when a name server is required.
Can someone please explain how name resolution works on a LAN/workgroup etc. ?
i.e. with Windows computer names I understand they do not need to be resolved i.e. you can just enter the computer name and connect, but if you then start to use exchange/AD servers etc, do you need a dns server to resolve them ?

Thanks for any clarification.

nathan

5695 posts

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#1178059 18-Nov-2014 17:47

Favourite search engine ->

Broadcast-Based Name Resolution, also known as B-Node name resolution

JWR

821 posts

Ultimate Geek

#1178146 18-Nov-2014 21:22

Active Directory requires DNS. It doesn't have to be Microsoft's DNS. But, it is easier (and generally better) that way.

Ragnor

8223 posts

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#1179510 19-Nov-2014 13:20

nathan: Favourite search engine

DuckDuckGo?

wasabi2k

2096 posts

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#1179519 19-Nov-2014 13:34

Windows computers do name resolution in a number of ways. The most common would be DNS, as that is used on the internet. This resolves names like www.google.com to IP addresses.

For most small workgroup setups the router will be doing DNS, so all your PCs will be pointing at that. You can see this by running ipconfig /all and checking what IP address is listed under DNS Servers. The router will proxy your DNS requests to your ISP's DNS, which it receives when it does the PPP IPCP handshaking when it logs on. It is also possible to point your clients directly at your ISP's DNS.

This is absolutely fine for external access, but won't resolve names of PCs on your local network, as the DNS services on routers normally don't let PCs register their names. In this case the PCs will usually fall back to older name resolution methods - namely broadcasts. The details of how this works depend a lot on the OS versions of your clients. Newer ones may use LLDP and the homegroup functions of windows, older ones just broadcast.

You can also deploy a WINS Server/Servers which handles netbios name resolution for older client OSes. It is basically a limited DNS but for NetBIOS names.

When you start getting to a LAN of any real size you need to handle DNS internally. Active Directory in particular requires DNS (and realistically Microsoft DNS is the sane way to do it) to be run on a server/servers locally and Exchange requires AD. Servers (and clients if required) then register their name records (and SRV records etc) with the DNS server locally and clients are pointed at the local DNS server(s) to resolve names. The local DNS servers can then be configured to forward external DNS requests outside to a public DNS server to allow name resolution for internet names. They can also be configured to query these themselves, but that is inefficient and comes with all the drawbacks of not using ISP DNS.

Glassboy

850 posts

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#1179567 19-Nov-2014 14:35

Hi there. To understand what name resolution is going to work you have to understand the network layer. If all of the hosts are (for example) on the same switch they are most likely going to be in the same broadcast domain (http://en.wikipedia.org/wiki/Broadcast_domain). Pretty much the host shouts "hey dave" and the targets says "what steve" and a conversation happens.

If the hosts aren't in the same broadcast domain, the host will need some kind of name resolution to work out where the target is. Analogous to Steve looking up Dave in a phone book. A local hosts file is Steve's personal address book, and DNS is the white pages. Obviously DNS is favoured because if the number changes then everyone gets to know, rather than multiple local files having to be updated.

What happens with the number is also analogous to a phone system, the host says to it's local router I want to this number and the router works out how to send the call through. It's actually all ARPs n' stuff, but all you need to know is ARP good, LARP bad. If someone asks you to LARP you should say no and tell them they are a bad person, LARPing is not a good way to network.