Slow Network

[Oliver Ruebenacker]

     Hello,

  Since two or three days, my network connection seems to have become
much slower. Loading websites with Firefox now takes a mutliple of the
time, and I am having sporadic "no mirrors found" errors with yum. I
am running F12 on a Dell Latitude D820 laptop, and I am connected by
wire to a router. There has been no noticeable change on two Windows
machines connected to the same router. All machines connect via DCHP.

  What can I do to diagnose or fix the problem? Thanks!

     Take care
     Oliver

-- 
Oliver Ruebenacker, Computational Cell Biologist
Systems Biology Linker at Virtual Cell (http://vcell.org/sybil)
Turning Knowledge Data into Models
Center for Cell Analysis and Modeling
http://www.oliver.curiousworld.org

[jack craig]

you might look at wireshark. its a very powerful tool.

as a beginning, you can do a trace on your lan and then use the exert 
mode to zero in on big issues...

just  a wag, ...

On 03/30/2010 12:06 PM, Oliver Ruebenacker wrote:
>        Hello,
>
>     Since two or three days, my network connection seems to have become
>  much slower. Loading websites with Firefox now takes a mutliple of the
>  time, and I am having sporadic "no mirrors found" errors with yum. I
>  am running F12 on a Dell Latitude D820 laptop, and I am connected by
>  wire to a router. There has been no noticeable change on two Windows
>  machines connected to the same router. All machines connect via DCHP.
>
>     What can I do to diagnose or fix the problem? Thanks!
>
>        Take care
>        Oliver
>
>      
-- 
Jack Craig
Software Engineer
831.461.7100 x120
www.extraview.com

[Tim]

On Tue, 2010-03-30 at 15:06 -0400, Oliver Ruebenacker wrote:
>    Since two or three days, my network connection seems to have
> become
>  much slower. Loading websites with Firefox now takes a mutliple of the
>  time, and I am having sporadic "no mirrors found" errors with yum. I
>  am running F12 on a Dell Latitude D820 laptop, and I am connected by
>  wire to a router. There has been no noticeable change on two Windows
>  machines connected to the same router. All machines connect via DCHP.
>   
>    What can I do to diagnose or fix the problem? Thanks! 
First obvious things:  The cable and connectors.  Try a different lead,
try a different socket on the router, inspect the socket on the laptop.

-- 
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored.  I
read messages from the public lists.

[Rick Stevens]

On 03/30/2010 12:06 PM, Oliver Ruebenacker wrote:
>        Hello,
>
>     Since two or three days, my network connection seems to have become
>  much slower. Loading websites with Firefox now takes a mutliple of the
>  time, and I am having sporadic "no mirrors found" errors with yum. I
>  am running F12 on a Dell Latitude D820 laptop, and I am connected by
>  wire to a router. There has been no noticeable change on two Windows
>  machines connected to the same router. All machines connect via DCHP.
>
>     What can I do to diagnose or fix the problem? Thanks! 
First, "ifconfig -a" and look at the error counts for each interface.
If you see a lot, then you start looking at hardware (bad cables, dirty
or loose connectors, flakey NICs, etc.).

If the errors look OK, have a look at your (DSL|cable) modem's
statistics and see if there's something odd going on at the WAN side
of things.  If using cable modem or DSL, you may need to reboot your
router and/or modem.  I make a habit of doing that every six months
or so.

If you're running nscd, purge your nscd DNS cache ("nscd -i hosts").
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, C2 Hosting          ricks(a)nerd.com -
- AIM/Skype: therps2        ICQ: 22643734            Yahoo: origrps2 -
-                                                                    -
-   Sarchasm: The gulf between the author of sarcastic wit and the   -
-                     reader...who doesn't get it.                   -
----------------------------------------------------------------------

[Oliver Ruebenacker]

     Hello,

On Tue, Mar 30, 2010 at 6:28 PM, Rick Stevens <ricks(a)nerd.com&gt; wrote:
>  On 03/30/2010 12:06 PM, Oliver Ruebenacker wrote:
> >       Hello,
> >
> >    Since two or three days, my network connection seems to have become
> > much slower. Loading websites with Firefox now takes a mutliple of the
> > time, and I am having sporadic "no mirrors found" errors with yum. I
> > am running F12 on a Dell Latitude D820 laptop, and I am connected by
> > wire to a router. There has been no noticeable change on two Windows
> > machines connected to the same router. All machines connect via DCHP.
> >
> >    What can I do to diagnose or fix the problem? Thanks!
>
>  First, "ifconfig -a" and look at the error counts for each interface.
>  If you see a lot, then you start looking at hardware (bad cables, dirty
>  or loose connectors, flakey NICs, etc.).
>
>  If the errors look OK, have a look at your (DSL|cable) modem's
>  statistics and see if there's something odd going on at the WAN side
>  of things.  If using cable modem or DSL, you may need to reboot your
>  router and/or modem.  I make a habit of doing that every six months
>  or so.
>
>  If you're running nscd, purge your nscd DNS cache ("nscd -i hosts").
  ifconfig shows no errors. I restarted the router and did nscd -i
hosts, and it got worse. Now, opening some pages (e.g. BBC News) takes
more than half a minute. The Windows machines connected to the same
router, on the other hand, load web pages just fine.

     Take care
     Oliver

-- 
Oliver Ruebenacker, Computational Cell Biologist
Systems Biology Linker at Virtual Cell (http://vcell.org/sybil)
Turning Knowledge Data into Models
Center for Cell Analysis and Modeling
http://www.oliver.curiousworld.org

[Rick Stevens]

On 03/31/2010 09:07 AM, Oliver Ruebenacker wrote:
>        Hello,
>
>  On Tue, Mar 30, 2010 at 6:28 PM, Rick Stevens<ricks(a)nerd.com>  wrote:
> > On 03/30/2010 12:06 PM, Oliver Ruebenacker wrote:
> >>        Hello,
> >>
> >>     Since two or three days, my network connection seems to have become
> >> much slower. Loading websites with Firefox now takes a mutliple of the
> >> time, and I am having sporadic "no mirrors found" errors with yum. I
> >> am running F12 on a Dell Latitude D820 laptop, and I am connected by
> >> wire to a router. There has been no noticeable change on two Windows
> >> machines connected to the same router. All machines connect via DCHP.
> >>
> >>     What can I do to diagnose or fix the problem? Thanks!
> >
> > First, "ifconfig -a" and look at the error counts for each interface.
> > If you see a lot, then you start looking at hardware (bad cables, dirty
> > or loose connectors, flakey NICs, etc.).
> >
> > If the errors look OK, have a look at your (DSL|cable) modem's
> > statistics and see if there's something odd going on at the WAN side
> > of things.  If using cable modem or DSL, you may need to reboot your
> > router and/or modem.  I make a habit of doing that every six months
> > or so.
> >
> > If you're running nscd, purge your nscd DNS cache ("nscd -i hosts").
>
>     ifconfig shows no errors. I restarted the router and did nscd -i
>  hosts, and it got worse. Now, opening some pages (e.g. BBC News) takes
>  more than half a minute. The Windows machines connected to the same
>  router, on the other hand, load web pages just fine. 
If you use DHCP, you need to restart the network bit on your Linux.
machine if you reboot the router.  The easiest way is to reboot the
system.  To do it manually:

	Network Manager: "sudo service NetworkManager restart"
	Classic Network: "sudo service network restart"

This will renew the DHCP lease, get a fresh IP and (hopefully) freshen
your /etc/resolv.conf file and gateway settings.  If you're using fixed
IPs, then a network restart probably isn't needed but it wouldn't hurt.

Next, sort out why it's taking so long.  My guess is a DNS issue, so
at the command line, try resolving the host name you're trying to
load, e.g. "host news.bbc.co.uk" or "nslookup news.bbc.co.uk".  They
should resolve pretty quickly.  If not, then you've found where the
holdup is.

If the name resolve takes too long, there's several possibilities.
One, your iptables is blocking DNS for some reason; two, you're not
using good DNS servers in your /etc/resolv.conf file.
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, C2 Hosting          ricks(a)nerd.com -
- AIM/Skype: therps2        ICQ: 22643734            Yahoo: origrps2 -
-                                                                    -
-                   To err is human, to moo bovine.                  -
----------------------------------------------------------------------

[Oliver Ruebenacker]

     Hello,

On Wed, Mar 31, 2010 at 12:50 PM, Rick Stevens <ricks(a)nerd.com&gt; wrote:
>  On 03/31/2010 09:07 AM, Oliver Ruebenacker wrote:
> >       Hello,
> >
> > On Tue, Mar 30, 2010 at 6:28 PM, Rick Stevens&lt;ricks(a)nerd.com&gt;  wrote:
> >> On 03/30/2010 12:06 PM, Oliver Ruebenacker wrote:
> >>>        Hello,
> >>>
> >>>     Since two or three days, my network connection seems to have become
> >>> much slower. Loading websites with Firefox now takes a mutliple of the
> >>> time, and I am having sporadic "no mirrors found" errors with yum.
> I
> >>> am running F12 on a Dell Latitude D820 laptop, and I am connected by
> >>> wire to a router. There has been no noticeable change on two Windows
> >>> machines connected to the same router. All machines connect via DCHP.
> >>>
> >>>     What can I do to diagnose or fix the problem? Thanks!
> >>
> >> First, "ifconfig -a" and look at the error counts for each interface.
> >> If you see a lot, then you start looking at hardware (bad cables, dirty
> >> or loose connectors, flakey NICs, etc.).
> >>
> >> If the errors look OK, have a look at your (DSL|cable) modem's
> >> statistics and see if there's something odd going on at the WAN side
> >> of things.  If using cable modem or DSL, you may need to reboot your
> >> router and/or modem.  I make a habit of doing that every six months
> >> or so.
> >>
> >> If you're running nscd, purge your nscd DNS cache ("nscd -i
> hosts").
> >
> >    ifconfig shows no errors. I restarted the router and did nscd -i
> > hosts, and it got worse. Now, opening some pages (e.g. BBC News) takes
> > more than half a minute. The Windows machines connected to the same
> > router, on the other hand, load web pages just fine.
>
>  If you use DHCP, you need to restart the network bit on your Linux.
>  machine if you reboot the router.  The easiest way is to reboot the
>  system.  To do it manually:
>
>         Network Manager: "sudo service NetworkManager restart"
>         Classic Network: "sudo service network restart" 
  Thank you, this time rebooting helped a lot. I think it is still
slower than usual, but definitely faster than before.

     Take care
     Oliver

-- 
Oliver Ruebenacker, Computational Cell Biologist
Systems Biology Linker at Virtual Cell (http://vcell.org/sybil)
Turning Knowledge Data into Models
Center for Cell Analysis and Modeling
http://www.oliver.curiousworld.org