Slow DNS Lookup - Debian

I've Google'd this problem plenty of times, but haven't seen many
current posts on the subject. Here's the deal:

A friend and I recently installed Linux on machines in our home
networks. I used Debian Testing, and he used Linspire (Debian based.)
We're now noticing that web pages take a VERY long time to load, the
DNS lookup inparticular. Even weirder, Windows XP PC's on the same
network load pages instantaneously!

I could be loosing my mind, but I swear it wasn't this way when I
loaded Debian onto this same PC about a year ago. The only advancement
I can imagine would be IPv6, which I've uninstalled from the Kernel
with "modconf"

My /etc/resolv.conf is as follows:
search ahvl.nc.charter.com
nameserver 192.168.1.10

The nameserver being my router of course. Anyway, any help is
appreciated. We've been trying to figure this out for a long time now.

- Henson

Are the Windows machines using the same DNS servers as the Linux boxes? Do the Windows machines have the DNS service running?

Whenever people on the broadbandreports.com forums complain of slow dns servers, people recommend using Level 3 communications servers.

They're 4.2.2.1, 4.2.2.2, and 4.2.2.3. Do a ping and see which is fastest for you, and try using that.

Hope that helps.

This is not limited to Debian-based distributions, but is a problem for
rpm distributions as well. In my experiments, I have run Fedora Core 1
and Fedora Core 4, Linspire 5-0, and SuSe 10.0. On every single one of
these distributions, loading webpages takes forever (or maybe even
longer, now that I think about it), and when I request a page I
typically see "Looking up [website].com" in the bottom-left corner of
Firefox for five-to-fifteen seconds before the page actually starts to
load. Once the page starts loading, however, data transfers quickly
and if the loading of data does go slowly it is because of bandwidth
issues. Pages which pull advertisements from external domains load
extremely slowly. I strongly believe that this is a DNS lookup issue;
I have no trouble downloading files and am extremely satisfied with the
speed of downloading very large files.

I pinged the IP addresses 4.2.2.1, 4.2.2.2, and 4.2.2.3 and for 4.2.2.1
I was returned a ping time of ~61-62 ms; for 4.2.2.2 I could ping at
~70 ms; 4.2.2.3 responded in ~60 ms. I set my DNS servers to 4.2.2.1
(primary) and 4.2.2.3 (secondary) to no avail; the connection still
takes forever.

Mrnull, what routers/firewalls are you behind? I have a Netopia Cayman
3347W DSL modem/router and a D-Link DI-624. I have tried disabling
firewalls for both of these devices, and the distro. I am currently
running SuSE 10.0. For what Microsoft Windows computers I do have in
the house the connection is snappy, even on the wireless network.

blue.zero1@gmail.com wrote:
> This is not limited to Debian-based distributions, but is a problem for
> rpm distributions as well. In my experiments, I have run Fedora Core 1
> and Fedora Core 4, Linspire 5-0, and SuSe 10.0. On every single one of
> these distributions, loading webpages takes forever (or maybe even
> longer, now that I think about it), and when I request a page I
> typically see "Looking up [website].com" in the bottom-left corner of
> Firefox for five-to-fifteen seconds before the page actually starts to
> load. Once the page starts loading, however, data transfers quickly
> and if the loading of data does go slowly it is because of bandwidth
> issues. Pages which pull advertisements from external domains load
> extremely slowly. I strongly believe that this is a DNS lookup issue;
> I have no trouble downloading files and am extremely satisfied with the
> speed of downloading very large files.
>
> I pinged the IP addresses 4.2.2.1, 4.2.2.2, and 4.2.2.3 and for 4.2.2.1
> I was returned a ping time of ~61-62 ms; for 4.2.2.2 I could ping at
> ~70 ms; 4.2.2.3 responded in ~60 ms. I set my DNS servers to 4.2.2.1
> (primary) and 4.2.2.3 (secondary) to no avail; the connection still
> takes forever.
>
> Mrnull, what routers/firewalls are you behind? I have a Netopia Cayman
> 3347W DSL modem/router and a D-Link DI-624. I have tried disabling
> firewalls for both of these devices, and the distro. I am currently
> running SuSE 10.0. For what Microsoft Windows computers I do have in
> the house the connection is snappy, even on the wireless network.

I don't know about the other distributions, but a number of SuSE 10.0
systems have been slow until they disabled IPV6. Apparently, every
lookup had to time out with IPV6 before the corresponding IPV4 address
was tried. Is this perhaps your difficulty?

Possibly. I'll try turning it off.

-blue.ze...@gmail.com

Larry Finger wrote:
> blue.zero1@gmail.com wrote:
> > This is not limited to Debian-based distributions, but is a problem for
> > rpm distributions as well. In my experiments, I have run Fedora Core 1
> > and Fedora Core 4, Linspire 5-0, and SuSe 10.0. On every single one of
> > these distributions, loading webpages takes forever (or maybe even
> > longer, now that I think about it), and when I request a page I
> > typically see "Looking up [website].com" in the bottom-left corner of
> > Firefox for five-to-fifteen seconds before the page actually starts to
> > load. Once the page starts loading, however, data transfers quickly
> > and if the loading of data does go slowly it is because of bandwidth
> > issues. Pages which pull advertisements from external domains load
> > extremely slowly. I strongly believe that this is a DNS lookup issue;
> > I have no trouble downloading files and am extremely satisfied with the
> > speed of downloading very large files.
> >
> > I pinged the IP addresses 4.2.2.1, 4.2.2.2, and 4.2.2.3 and for 4.2.2.1
> > I was returned a ping time of ~61-62 ms; for 4.2.2.2 I could ping at
> > ~70 ms; 4.2.2.3 responded in ~60 ms. I set my DNS servers to 4.2.2.1
> > (primary) and 4.2.2.3 (secondary) to no avail; the connection still
> > takes forever.
> >
> > Mrnull, what routers/firewalls are you behind? I have a Netopia Cayman
> > 3347W DSL modem/router and a D-Link DI-624. I have tried disabling
> > firewalls for both of these devices, and the distro. I am currently
> > running SuSE 10.0. For what Microsoft Windows computers I do have in
> > the house the connection is snappy, even on the wireless network.
>
> I don't know about the other distributions, but a number of SuSE 10.0
> systems have been slow until they disabled IPV6. Apparently, every
> lookup had to time out with IPV6 before the corresponding IPV4 address
> was tried. Is this perhaps your difficulty?

You know what? That did it. Thank you, this has been driving me nuts.

But I have one question, and this comes from a complete know-nothing
when it comes to networking, so bear with me. IPv6 seems like such a
cool new thing. I think this should work. I mean, IPv6 shouldn't
cause any trouble with my networking. I mentioned earlier that I was
behind a Netopia Cayman 3347W dslmodem/router and a D-Link DI-624
wireless G router, but when IPv6 is enabled without the D-Link wireless
router, my DNS Lookup still goes slow (so I think we can rule out the
D-Link). Is this because of the Cayman? Here is a technical spec
sheet: http://www.netopia.com/equipment/pdf/spec/3300w.pdf (according
to Netopia Support, this document applies to my model). Perhaps the
router is too old,
http://netopia.com/support/resources/option_3347w.html I can't remember
the manufacturing date, but I am pretty sure it was before IPv6.

TechsysPete wrote:
> Larry Finger wrote:
>
>>blue.zero1@gmail.com wrote:
>>
>>>This is not limited to Debian-based distributions, but is a problem for
>>>rpm distributions as well. In my experiments, I have run Fedora Core 1
>>>and Fedora Core 4, Linspire 5-0, and SuSe 10.0. On every single one of
>>>these distributions, loading webpages takes forever (or maybe even
>>>longer, now that I think about it), and when I request a page I
>>>typically see "Looking up [website].com" in the bottom-left corner of
>>>Firefox for five-to-fifteen seconds before the page actually starts to
>>>load. Once the page starts loading, however, data transfers quickly
>>>and if the loading of data does go slowly it is because of bandwidth
>>>issues. Pages which pull advertisements from external domains load
>>>extremely slowly. I strongly believe that this is a DNS lookup issue;
>>>I have no trouble downloading files and am extremely satisfied with the
>>>speed of downloading very large files.
>>>
>>>I pinged the IP addresses 4.2.2.1, 4.2.2.2, and 4.2.2.3 and for 4.2.2.1
>>>I was returned a ping time of ~61-62 ms; for 4.2.2.2 I could ping at
>>>~70 ms; 4.2.2.3 responded in ~60 ms. I set my DNS servers to 4.2.2.1
>>>(primary) and 4.2.2.3 (secondary) to no avail; the connection still
>>>takes forever.
>>>
>>>Mrnull, what routers/firewalls are you behind? I have a Netopia Cayman
>>>3347W DSL modem/router and a D-Link DI-624. I have tried disabling
>>>firewalls for both of these devices, and the distro. I am currently
>>>running SuSE 10.0. For what Microsoft Windows computers I do have in
>>>the house the connection is snappy, even on the wireless network.
>>
>>I don't know about the other distributions, but a number of SuSE 10.0
>>systems have been slow until they disabled IPV6. Apparently, every
>>lookup had to time out with IPV6 before the corresponding IPV4 address
>>was tried. Is this perhaps your difficulty?
>
>
> You know what? That did it. Thank you, this has been driving me nuts.
>
> But I have one question, and this comes from a complete know-nothing
> when it comes to networking, so bear with me. IPv6 seems like such a
> cool new thing. I think this should work. I mean, IPv6 shouldn't
> cause any trouble with my networking. I mentioned earlier that I was
> behind a Netopia Cayman 3347W dslmodem/router and a D-Link DI-624
> wireless G router, but when IPv6 is enabled without the D-Link wireless
> router, my DNS Lookup still goes slow (so I think we can rule out the
> D-Link). Is this because of the Cayman? Here is a technical spec
> sheet: http://www.netopia.com/equipment/pdf/spec/3300w.pdf (according
> to Netopia Support, this document applies to my model). Perhaps the
> router is too old,
> http://netopia.com/support/resources/option_3347w.html I can't remember
> the manufacturing date, but I am pretty sure it was before IPv6.
>

I don't know that much either as I was just reporting what I had read.
My guess is that IPV6 works well if it is enables end-to-end, but if
there is an IPV4-only link anywhere between your DNS client and the DNS
server, then there will be a timeouts such as you observed. AFAIK, my
Linksys WRT54G wireless AP/router knows nothing of IPV6 - at least I
couldn't find any menu entries that refer to it.

I will contact my ISP and see if I can trade in my Cayman for a newer
model. If I can, I will enable IPv6 again and report what I find.
I've tried linux on more than one of my computers, several in fact,
with this problem consistently showing up.

On Mon, 05 Dec 2005 10:25:28 -0800, mrnull wrote:

> I've Google'd this problem plenty of times, but haven't seen many
> current posts on the subject. Here's the deal:
>
> A friend and I recently installed Linux on machines in our home
> networks. I used Debian Testing, and he used Linspire (Debian based.)
> We're now noticing that web pages take a VERY long time to load, the
> DNS lookup inparticular. Even weirder, Windows XP PC's on the same
> network load pages instantaneously!
>
> I could be loosing my mind, but I swear it wasn't this way when I
> loaded Debian onto this same PC about a year ago. The only advancement
> I can imagine would be IPv6, which I've uninstalled from the Kernel
> with "modconf"
>
> My /etc/resolv.conf is as follows:
> search ahvl.nc.charter.com
> nameserver 192.168.1.10
>
> The nameserver being my router of course. Anyway, any help is
> appreciated. We've been trying to figure this out for a long time now.
>
> - Henson

There are two issues which affect DNS lookups. One is - disable IPV6. The
second is that some DNS servers seem to miss the first couple of requests
from Linux machines. The default timeout is five seconds, so this
frequently results in about a 10-12 second time lag (the IPV6 lag can be
about 30 seconds). To fix this issue, add

option timeout:1

to the /etc/resolv.conf file.

On 6 Dec 2005, in the Usenet newsgroup comp.os.linux.networking, in article
<1133883263.207820.79440@g49g2000cwa.googlegroups. com>, TechsysPete wrote:

>But I have one question, and this comes from a complete know-nothing
>when it comes to networking, so bear with me. IPv6 seems like such a
>cool new thing. I think this should work. I mean, IPv6 shouldn't
>cause any trouble with my networking.

Depends on the name server and client you are using. You can ask the
name server for an AA record, and it may respond with a 'NXDOMAIN'
(which means there is no such record), a 'SERVFAIL' (which means it was
not able to resolve the request remotely, or 'NOTIMP' (which often means
it doesn't understand what you are asking), or it may not respond at all.
The way to find that would be to use tcpdump. Often, the way Linux distros
are setting up resolvers now is to prefer IPv6 if it is not disabled. Only
if/when an AA query fails (or times out) does it try a IPv4 'A' query.

You're posting out of BellSouth space in the USA.

[compton ~]$ grep US P.ADDR/stats/delegated-arin-20051115 | grep -c ipv4
31315
[compton ~]$ grep US P.ADDR/stats/delegated-arin-20051115 | grep -c ipv6
197
[compton ~]$

31000 IPv4 networks in the US, 197 IPv6. IPv6 is the coming thing, but
that doesn't mean it is here now.

Old guy