DNS questions
in [Linux Networking]
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From: steve on 2 Mar 2010 10:11 We are having some problems with our Linux DNS computer on a windows network. Most sites we can get to but others we cannot. The site comes up not found. One of the simple questions I have is how can I know when I change the dns address if its working. In other words, Its my understading that I simply need to add to the file /etc/resolv.conf a line like nameserver 8.8.8.8 And that affectively adds the dns number. However Does this change the moment I add this line to the file. Or is there somethign else I need to do. eg if I start to suf the web from a windows machine that is using this linux comptuer as a dns is it changed. I have looked high and low for a command to tell me what the (active) dns is on linux and the only responses I can find are look in the resolv.conf file. But just becasue its in the resolv.conf file doesnt mean its using this NEW dns number. (unless that the way it works.) I wish there was a commadn line in windows like ipconfig /all which shows it. Is the such a command in linux? or if its in the resolve file does it just work? By the way here are my nslookup results. the web site itravel2000.com (amonst others we cant get to ) But google we can.?? > [root(a)smclinux ~]# nslookup itravel2000.com ;; connection timed out; no servers could be reached [root(a)smclinux ~]# nslookup www.google.com Server: 192.168.1.1 Address: 192.168.1.1#53 Non-authoritative answer: www.google.com canonical name = www.l.google.com. Name: www.l.google.com Address: 74.125.95.99 Name: www.l.google.com Address: 74.125.95.104 Name: www.l.google.com Address: 74.125.95.105 Name: www.l.google.com Address: 74.125.95.147 Name: www.l.google.com Address: 74.125.95.106 Name: www.l.google.com Address: 74.125.95.103 [root(a)smclinux ~]#
From: Chris Davies on 2 Mar 2010 17:59 steve <stevesemple(a)lycos.com> wrote: > We are having some problems with our Linux DNS computer on a windows > network. > In other words, Its my understading that I simply need to add to the > file /etc/resolv.conf a line like > nameserver 8.8.8.8 > And that affectively adds the dns number. Pretty much, yes. If you're trying to debug this stuff make sure you've removed (or commented out) any other nameserver entry here. Also, be aware that /etc/resolv.conf can be updated via DHCP, so your change may get overwritten. (There are ways round this, but its out of scope for now.) > However Does this change the moment I add this line to the file. Or > is there somethign else I need to do. It changes from the instant you write out the new version of the file. > eg if I start to suf the web from a windows machine that is > using this linux comptuer as a dns is it changed. In most instances the DNS is checked via /etc/resolv.conf each time you need a name resolved. Obvious exceptions are when you're using a web proxy, or when DNS is configured to use your Windows WINS service for name resolution. > I have looked high and low for a command to tell me what the (active) > dns is on linux and the only responses I can find are look in the > resolv.conf file. Provided that names are being resolved via DNS, this is correct. But names can also be resolved via other services - and also in the file /etc/hosts. The *usual* networked method is to look names up using DNS. > But just becasue its in the resolv.conf file doesnt mean its using this > NEW dns number. (unless that the way it works.) I wish there was a > commadn line in windows like ipconfig /all which shows it. Is the such > a command in linux? or if its in the resolve file does it just work? It just works. > By the way here are my nslookup results. the web site itravel2000.com > (amonst others we cant get to ) But google we can.?? > [root(a)smclinux ~]# nslookup itravel2000.com > ;; connection timed out; no servers could be reached > [root(a)smclinux ~]# nslookup www.google.com > Server: 192.168.1.1 > Address: 192.168.1.1#53 Is 192.168.1.1 your linux box? If not, then you need to look there for your DNS resolving problem, first. Chris
From: GangGreene on 2 Mar 2010 18:04 steve wrote: > In other words, Its my understading that I simply need to add to the > file /etc/resolv.conf a line like Correct > > nameserver 8.8.8.8 > And that affectively adds the dns number. However Does this change the > moment I add this line to the file. Or is there somethign else I need > to do. eg if I start to suf the web from a windows machine that is > using this linux comptuer as a dns is it changed. I have looked high > and low for a command to tell me what the (active) dns is on linux and > the only responses I can find are look in the resolv.conf file. But > just becasue its in the resolv.conf file doesnt mean its using this > NEW dns number. (unless that the way it works.) I wish there was a > commadn line in windows like ipconfig /all which shows it. Is the such > a command in linux? or if its in the resolve file does it just work? > Immediate > By the way here are my nslookup results. the web site itravel2000.com > (amonst others we cant get to ) > But google we can.?? > >> [root(a)smclinux ~]# nslookup itravel2000.com > ;; connection timed out; no servers could be reached Your DNS server is not working/faulty $ nslookup itravel2000.com Server: 192.168.1.6 Address: 192.168.1.6#53 Non-authoritative answer: Name: itravel2000.com Address: 66.252.144.103 > > [root(a)smclinux ~]# nslookup www.google.com > Server: 192.168.1.1 > Address: 192.168.1.1#53 > > Non-authoritative answer: > www.google.com canonical name = www.l.google.com. > Name: www.l.google.com
From: David Schwartz on 3 Mar 2010 02:50 On Mar 2, 7:11 am, steve <stevesem...(a)lycos.com> wrote: > In other words, Its my understading that I simply need to add to the > file /etc/resolv.conf a line like > > nameserver 8.8.8.8 > And that affectively adds the dns number. To this machine's resolver. > However Does this change the > moment I add this line to the file. It's instant, unless you are running a DNS cache of some kind. If you're running a DNS cache, you should flush it. > Or is there somethign else I need > to do. eg if I start to suf the web from a windows machine that is > using this linux comptuer as a dns is it changed. It will have no effect on the name server on this computer, only on the resolver, unless you are using a nameserver that uses the system resolver. Some don't (such as bind) and some do (such as dropbear). DS
From: steve on 4 Mar 2010 10:28 thanks Im going to have to do some more research and probably get back to this group for further help.
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