工作学习 / 专业技术讨论 / [ quiz ] a Unix box was able to nslookup www.yahoo.com, but could neither browse the web w/o a proxy server nor ping any valid hostnames. What was the problem?
-spiral(Tuesday);
2006-1-26(#2748270@0)
nslookup just checks DNS server, or even just local cache without network avaiable. It doesn't mean the box has correct setting on gateway or other parts of TCP/IP to access that host/server.
-liyaot(Rick);
2006-1-26{340}(#2748336@0)
nslookup just checks DNS server, or even just local cache without network avaiable. It doesn't mean the box has correct setting on gateway or other parts of TCP/IP to access that host/server. eg. your standalone box with w3.ibm.com in your /etc/hosts. nslookup can find it, but it has no mean the box can ping to that ibm intranet IP.
You're close, but not on the right track.. it's a box on the internet... anything you can think of ?
-spiral(Tuesday);
2006-1-26(#2748341@0)
traceroute, ping ip, tcpdump, telnet ip:80 or 8080 can help you
-falcon(令狐葱);
2006-1-26(#2748337@0)
hint: nothing works except nslookup for any valid host names...
-spiral(Tuesday);
2006-1-26(#2748339@0)
"nothing works" is too vague...what's the err msg when you try the following: traceroute host/ip, ping host/ip, telnet host/ip:80 or 8080 ?
-falcon(令狐葱);
2006-1-26{137}(#2748344@0)
what is your /etc/nsswitch.conf, what is your /etc/resolv.conf, what does it tell you if you type nslookup ? , what about nslookup>server
resolv.conf gives a few lines of correct dns server ip's... and?
-spiral(Tuesday);
2006-1-27(#2748348@0)
too little info.....give all output first.....
-falcon(令狐葱);
2006-1-27(#2748351@0)
it means none of the other network depend applications works... mail, traceroute, ping, browser, ssh, telnet, ftp,,, almost any thing one can think of, except nslookup or dig... ;-)
-spiral(Tuesday);
2006-1-27(#2748350@0)
if I put it in my local host file, and unplug the cable, I can still nslookup, but can't go anywhere.....is this what it's all about ?
-falcon(令狐葱);
2006-1-27(#2748354@0)
okay, I didn't make it clear. The /etc/hosts file doesn't have much in it, you can nslookup any valid hostnames that are not in the /etc/hosts... ...
-spiral(Tuesday);
2006-1-27(#2748361@0)
Can you ping yourself? Or can you ping 127.0.0.1? What name server were you using when you were using nslookup, local one or internet one?
-haoxia74(haoxia);
2006-1-27(#2748394@0)
yes I can ping myself or any valid host ip, the dns server is not local...
-spiral(Tuesday);
2006-1-27(#2748403@0)
/etc/host.conf.
From what you described,I guess bind is missing in "order hosts,bind" in the above file
-haoxia74(haoxia);
2006-1-27(#2748465@0)
There's no host.conf, but you're really close...
-spiral(Tuesday);
2006-1-27(#2749078@0)
/etc/nsswitch.conf :-) I bet I am right this time.
Thanks for your interesting quiz.
-haoxia74(haoxia);
2006-1-27(#2749477@0)
to be fair, the problem was solved only after i looked at one file... the answer will be given after 2 days... just curious if any high-hands can tell w/o seeing this file...
-spiral(Tuesday);
2006-1-27(#2748395@0)
please allow me to add that the proxy server I provided to the browser was an ip address...
-spiral(Tuesday);
2006-1-27(#2748417@0)
Here is answer for you. There is a firewall block all the traffic except the tcp or UDP traffic for port 53. The other answer would be:
-bugfree(BugFree);
2006-1-27{203}(#2748448@0)
The company firewall block all other IP address traffic except the DNS server. Then that DNS can do recursive query to his root server without any problem. But your workstation can not access interest ;)
and you didn't even read the first post carefully. "could neither browse the web w/o a proxy server" which means "could browse the web with a proxy server"
-guestagain(guest again);
2006-1-27(#2748502@0)
What I can think is to check files: /etc/nsswitch.conf and /etc/resolv.conf
-kisswolf(土狼一号);
2006-1-27(#2749919@0)