Slow Host Resolving

zen · 2009-09-04 07:51:20

I've discovered another unusual issue that i'm kind of in the dark about.

When I load a website, it sits for what seems like forever 'Resolving Host'. then, when it's done, the site loads like normal. Here's what I dont get. If I go to other webpages that are part of the same .com address, it loads like normal, very quick, like it should.. But, if I change to a different site (or anything with a different <something>.com, it takes forever to 'resolve host' again.

After searching the forums, I tried "sysctl -w net.ipv4.tcp_timestamps=0", but didn't notice any change, so I reverted back to the default.

To me it sounds like a DNS issue of some kind...but I could be wrong. The other kicker... when I ping websites, my ping time is not higher then normal, that comes back as fast as it should, which eliminates a problem with ipv6 ... i think.

This occurs in Konqurer, Firefox, and Chromium, so it's not program specific. I had this same problem in Fedora 11 (previous distro) using firefox as well, but no issues with windows 7 RC/ubuntu (used prior to fedora).

Any ideas?

gaten · 2009-09-04 08:00:44

What about changing dns servers and see if that changes anything? I found when I switched to OpenDNS, everything seemed to resolve just a bit quicker.

http://www.opendns.com/

Also, what are your dns servers now?

zen · 2009-09-04 08:23:43

Well, I have a 4mb DSL line, and it's configured through DHCP. My dns server's I use would probably be my ISPs. It's a local ISP, and it's normally almost instantaneous.

I'll look into opendns, but i'm also going to burn an ubuntu livecd quick. I dont remember having the problem in windows or ubuntu prior. It started with fedora, which I just thought was an issue with firefox, but apparently not...

It seems like the DNS servers are working correctly though, here's an example.

I load myspace.com, and wait for the host to resolve and load. Once it's loaded, if i click on terms, or privacy policy, they both load extremely fast, because the URLs are myspace.com/something. However, if I click on jobs, it takes forever to resolve the host again because it changes from www.myspace.com/anything to jobs.myspace.com. If i click back on privacy policy, it takes forver to resolve the DNS again.

The other possibility is it may be something with the firmware of my modem/router and may have a full buffer or something. If the problem continues on a livecd, then I know it's either DNS problem, ISP problem, or modem problem. I'll try that and post back the results.

Thanks for the idea though, everything helps.

shining · 2009-09-04 09:36:32

zen wrote:

To me it sounds like a DNS issue of some kind...but I could be wrong. The other kicker... when I ping websites, my ping time is not higher then normal, that comes back as fast as it should, which eliminates a problem with ipv6 ... i think.
Any ideas?

I have no ideas, but just in case, I would try disabling ipv6 anyway. just to be 100% sure.
Changing dns servers is also very easy to try.

You just need a few seconds to try.

zen · 2009-09-04 17:23:12

UPDATE - Problem still exists

I switched to the opendns servers with no noticable improvement (atleast not for the problem I was having). I also contacted my ISP and they pushed the most recent firmware update for the modem/router combination that i'm using to eliminate that as a cause, and that also made no difference aside from providing a rather important security fix that I wish they had let me know about when it was released...

So.. I'll look around to find out how to disable ipv6 and see what that does... I haven't tried a different distro (via live cd) to see if the problem is related to something else in the setup or not yet, didn't want to waste a dvd-r on that just yet, lol

zen · 2009-09-04 17:34:50

UPDATE - [Solved]

Finally, my internet is restored to it's old screaming self.

by adding "alias net-pf-10 off" to my modprobe.conf and rebooting, that seems to have disabled the auto-loading of the ipv6 module. Sweet!

Now, a final question since I have no experience with opendns.

Since the dns server isn't local (I.E. not hosted by my isp), wouldn't it stand to reason that it would be slower to use opendns because there is a longer path from me to the servers?

Meyithi · 2009-09-04 17:48:45

Are you cache'ing DNS queries?

http://wiki.archlinux.org/index.php/Spe … th_dnsmasq

shining · 2009-09-04 17:49:52

zen wrote:

UPDATE - [Solved]
Finally, my internet is restored to it's old screaming self.
by adding "alias net-pf-10 off" to my modprobe.conf and rebooting, that seems to have disabled the auto-loading of the ipv6 module. Sweet!
Now, a final question since I have no experience with opendns.
Since the dns server isn't local (I.E. not hosted by my isp), wouldn't it stand to reason that it would be slower to use opendns because there is a longer path from me to the servers?

so it was indeed an ipv6 issue again ?
ipv6 is always the first suspect in case of slow dns issues

I would indeed think that isp dns are supposed to be faster than external dns, unless they are broken. But I am not a network expert ...

zen · 2009-09-04 17:52:48

I'm not currently caching DNS querys locally, but I found out how to benchmark performance to determine if opendns is faster then my isp provided dns.

the command from a dos prompt is nslookup.

Is there a linux equivalent to that command so I can time a dns query?

And yep, ipv6 was the cause, I never knew it was loaded automatically and I never knew that ipv6 is tried before ipv4 is tried, which is what caused the lag time.

Last edited by zen (2009-09-04 17:57:19)

tempo · 2010-01-14 10:48:17

zen wrote:

UPDATE - [Solved]
Finally, my internet is restored to it's old screaming self.
by adding "alias net-pf-10 off" to my modprobe.conf and rebooting, that seems to have disabled the auto-loading of the ipv6 module. Sweet!
Now, a final question since I have no experience with opendns.
Since the dns server isn't local (I.E. not hosted by my isp), wouldn't it stand to reason that it would be slower to use opendns because there is a longer path from me to the servers?

your method doesn't work for me ......

tempo · 2010-01-14 11:23:21

my solution is to add
Nameserver : 208.67.222.222 and 208.67.220.220 in /etc/resolv.conf.

(before i added "alias net-pf-10 off" to my modprobe.conf and rebooting, but no use)

this post has other suggestion
http://bbs.archlinux.org/viewtopic.php? … 60#p688060

Last edited by tempo (2010-01-14 11:27:04)

T-u-N-i-X · 2010-01-14 12:33:34

GNOME Public DNS is even faster than OpenDNS.

Arch Linux

#1 2009-09-04 07:51:20

Slow Host Resolving

#2 2009-09-04 08:00:44

Re: Slow Host Resolving

#3 2009-09-04 08:23:43

Re: Slow Host Resolving

#4 2009-09-04 09:36:32

Re: Slow Host Resolving

#5 2009-09-04 17:23:12

Re: Slow Host Resolving

#6 2009-09-04 17:34:50

Re: Slow Host Resolving

#7 2009-09-04 17:48:45

Re: Slow Host Resolving

#8 2009-09-04 17:49:52

Re: Slow Host Resolving

#9 2009-09-04 17:52:48

Re: Slow Host Resolving

#10 2010-01-14 10:48:17

Re: Slow Host Resolving

#11 2010-01-14 11:23:21

Re: Slow Host Resolving

#12 2010-01-14 12:33:34

Re: Slow Host Resolving

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