Linux - NetworkingThis forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.
Notices
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
I'm running Ubuntu 9.10 and experiencing slow DNS resolution over a wired connection, even running a vanilla kernel without ipv6 capability. I've disabled ipv6 in firefox, changed my DNS servers (tried 4.2.2.1 and OpenDNS), upgraded to beta Tomato firmware for my linksys router, tried disabling the nonexistent ipv6 modules, tried pdnsd, all to no avail. Anyone else have any other suggestions? DNS resolution is fine when the computer is either connected directly to the modem or in Windows 7. Also, my 9.10 laptop works fine with wireless on the same router. Any help would be appreciated
"wired" as opposed to wireless, so using an ethernet cable I guess. By "connected directly" I mean bypassing my router and connecting directly to my cable modem.
"wired" as opposed to wireless, so using an ethernet cable I guess. By "connected directly" I mean bypassing my router and connecting directly to my cable modem.
In what way is it slow? What does a tcpdump of a single DNS resolution look like? Is it retrying? Trying different servers? What are you actually doing to pinpoint a DNS issue in the first place? host/dig/nslookup i would hope.
Dice, you can use 'host -a' to see the time involved with resolving a name, which shows up at the bottom of the results.
Code:
jcwx@haley:~$ host -a google.com 24.196.64.53
Trying "google.com"
Using domain server:
Name: 24.196.64.53
Address: 24.196.64.53#53
Aliases:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52127
;; flags: qr rd ra; QUERY: 1, ANSWER: 14, AUTHORITY: 4, ADDITIONAL: 7
;; QUESTION SECTION:
;google.com. IN ANY
;; ANSWER SECTION:
google.com. 247 IN MX 400 google.com.s9b2.psmtp.com.
google.com. 247 IN MX 100 google.com.s9a1.psmtp.com.
google.com. 247 IN MX 200 google.com.s9a2.psmtp.com.
google.com. 247 IN MX 300 google.com.s9b1.psmtp.com.
google.com. 216 IN A 74.125.95.104
google.com. 216 IN A 74.125.95.105
google.com. 216 IN A 74.125.95.106
google.com. 216 IN A 74.125.95.147
google.com. 216 IN A 74.125.95.99
google.com. 216 IN A 74.125.95.103
google.com. 231122 IN NS ns4.google.com.
google.com. 231122 IN NS ns2.google.com.
google.com. 231122 IN NS ns3.google.com.
google.com. 231122 IN NS ns1.google.com.
;; AUTHORITY SECTION:
google.com. 231122 IN NS ns4.google.com.
google.com. 231122 IN NS ns1.google.com.
google.com. 231122 IN NS ns3.google.com.
google.com. 231122 IN NS ns2.google.com.
;; ADDITIONAL SECTION:
google.com.s9a1.psmtp.com. 13160 IN A 74.125.148.10
google.com.s9a2.psmtp.com. 8574 IN A 74.125.148.11
google.com.s9b1.psmtp.com. 3929 IN A 74.125.148.13
google.com.s9b2.psmtp.com. 1587 IN A 74.125.148.14
ns1.google.com. 36325 IN A 216.239.32.10
ns2.google.com. 33786 IN A 216.239.34.10
ns3.google.com. 54712 IN A 216.239.36.10
Received 498 bytes from 24.196.64.53#53 in 25 ms
jcwx@haley:~$
The 24.196.64.53 address at the end of the command is a DNS server. You can leave that off and whatever is defined in resolv.conf will be used. That should allow you to quantify the delays you are experiencing. You might try this on your firewall/router as well, although I'm using OpenWRT, and the host command isn't installed. Your firmware might have it.
If you firewall is resolving well, you might consider setting up dnsmasq on it. It works well on OpenWRT. In reality, though, you really shouldn't be having any issues with DNS like you describe. You could run a tcpdump capture to see the traffic itself. Could provide a clue as to what is going on:
tcpdump -s 0 -vvvnni eth1 port 53 or icmp
Replace the interface with whatever applies in your situation. You can run that on your firewall as well as your local system. The icmp could provide messages indicating there is a network related problem.
I was looking at nslookup, and there is a debug mode that could provide some insight into potential DNS issues. dig has plenty of command line options, too.
Code:
jcwx@haley:~$ nslookup
> set debug
> set d2
> slackware.com
addlookup()
make_empty_lookup()
looking up slackware.com
start_lookup()
setup_lookup(0x272de00)
resetting lookup counter.
(cut for the sake of brevity)
------------
detailsection()
QUESTIONS:
slackware.com, type = A, class = IN
detailsection()
ANSWERS:
-> slackware.com
internet address = 64.57.102.34
detailsection()
AUTHORITY RECORDS:
detailsection()
ADDITIONAL RECORDS:
------------
Non-authoritative answer:
printsection()
Name: slackware.com
Address: 64.57.102.34
still pending.
cancel_lookup()
check_if_done()
list empty
clear_query(0xb76b8010)
sockcount=0
check_next_lookup(0x272de00)
try_clear_lookup(0x272de00)
destroy
freeing server 0x271b200 belonging to 0x272de00
start_lookup()
check_if_done()
list empty
shutting down
dighost_shutdown()
unlock_lookup dighost.c:3315
>
Could help. Good luck.
Last edited by devwatchdog; 02-16-2010 at 09:51 PM.
I'm so sorry LQ, I was out of the country for a while and then forgot to check the responses to this thread. Unfortunately my computer is still symptomatic: it's slow to load web pages in firefox and opera. It can handle sustained connections for gaming and such with no problems besides an initial pause.
Confusingly, DNS resolution is very fast using dig/nslookup/host. I still have no problems on the same machine with Windows 7. I assumed that I had a DNS issue because of other Ubuntu threads and also firefox's status bar message, "Looking up (site)..."
resolv.conf:
# Generated by NetworkManager
nameserver 192.168.1.1
nameserver 4.2.2.2
Looking at tcpdump on port 53 while entering a site into opera, I noticed that it takes a long time (10-15 seconds) for any traffic to show up, but once it does the page loads quickly. Any thoughts?
If dig/nslookup/host are very fast but Opera and Firefox are not (as shown by "Looking up (site)..." and tcpdump then Opera and Firefox are probably using different name resolution methods from dig/nslookup/host.
Not something I know a lot about so I can't help much further but hopefully the pointer is some help.
Might be worth posting your nsswtch.conf (but dig/nslookup/host probably use that so it may not help) -- elsewise time to investigate how the browsers are configured to do name resolution.
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.
