Red Hat Bugzilla – Bug 154599
Extremely slow name resolution, throughput is fine
Last modified: 2015-01-04 17:18:42 EST
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User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050328 Firefox/1.0.2 Fedora/1.0.1-1.3.1 StumbleUpon/1.9992
Description of problem:
I am getting lots of timeouts when trying to browse the web. Once I get a website loaded, it is generally fast, but loading the first page sometimes takes several tries.
I dual-boot with Windows XP and although there are some blips in service, they are nowhere near as noticeable as those under Linux.
This problem also appeared while running Mandrake 10.2
There are no problems with connecting to other computers on our LAN
Version-Release number of selected component (if applicable):
Steps to Reproduce:
-bash-3.00# nslookup arstechnica.com
;; connection timed out; no servers could be reached
-bash-3.00# nslookup arstechnica.com
My DNS servers are provided by Verizon:
3Com Corporation 3c905C-TX/TX-M [Tornado]
DNS settings (From network configuration)
Primary DNS: 126.96.36.199
Secondary DNS: 188.8.131.52
DNS search path: localdomain
Automatically obraining IP address settings from dhcp
Automatically obtaining DNS information from provider
IPv6 configuration is off
what does /etc/resolv.conf look like ?
can you capture with tcpdump/tethereal a packet dump showing what happens when
you do a lookup ?
[greg@localhost ~]$ cat /etc/resolv.conf
; generated by /sbin/dhclient-script
A little more on what happens:
Browsing works fine, everything is fast. Then at random times, it breaks.
The other Windows and FC machines all can't get out to the internet. Maybe
it's just DNS, maybe it's everything. Not sure yet. Anyway, after a little
while, the Windows machines are back to browsing the internet at normal
speeds, but the FC machines are still getting timeouts when browsing to new
sites. If I am able to connect to a download site with one of the FC machines
though, the download will happen at full speed.
Tomorrow I will try out using different DNS servers; see what that does.
When the problem happens again, I'll post the tethereal dump as requested.
Thank you for taking the time to work with me on this one. I know this is one
of those problems that are near impossible to pin down, and it seems like
one of those times where the user just doesn't know what they're doing,
so I just wanted to commend you for helping me. Truely great support!
Actually, I've seen something similar with my dsl at home, which is also
provided by Verizon. From time to time the modem seems to 'forget' the MAC
address of the remote end of the connection.
If you run tcpdump, you'll see lots of outgoing ARP who-has traffic, followed by
a flood of responses a while later.
The modem they provided me with is a Westell (dont have the model # handy).
Do you have the same one by any chance ?
My suspicion is that this isn't a Linux problem (I see the same thing with my
Wife's Apple Powerbook), but some problem either with Verizons end of the DSL,
or the modem firmware.
Created attachment 113267 [details]
tethereal capture of an outage
Here's the tethereal output when I tried to visit
At first it fails, but I kept refreshing until it went through.
I tried to cut out background noise like kmail checking for mail; let me know
if I cut too much.
I guess 192.168.0.113 is your desktop machine, what is 192.168.0.1 ?
If this is your modem, I'm stuck.
If its a Linux firewall/gateway, can you run the tethereal there instead ?
you can make things slightly faster by disabling ipv6 if you don't use it..
alias net-pf-10 off
to your /etc/modprobe.conf, and next time you boot your interfaces won't be IPV6
192.168.0.113 -> my computer (now on FC3)
192.168.0.120 -> another FC3 computer
192.168.0.1 -> D-Link DI-704P router (http://www.dlink.com/products/?pid=63)
I have had problems with small SOHO routers. To save costs they are often
designed and tested with only windows in mind where windows uses shorter, non
standard timeouts and other network idosyncracies. They are also designed for
only 4 NATed internal hosts so if you have more than 4 internal hosts you get
Are you using it as a firewall ?
Are you using NAT ?
Do you have more than 4 internal hosts ?
If I ever come up with some clear test case, I'll reopen. Otherwise, this is
Thanks for all your help though :)