Traceroute/ping help

Traceroute/ping help

Post by E » Thu, 09 May 2002 05:36:47



Hi - currently have cable modem service with Charter.  Service has
gotten really bad recently - very intermittent.  I called them up to
complain, but they said there was nothing wrong.  I'm trying to get
armed with more information so that I can specifically point out what
the problem is.  I'm not all that familiar with unix networking, so
you'll have to bear with me.

I have a router running redhat, and some machines with static IP's
connected to it.  Starting at the router level, I did a traceroute to
www.yahoo.com (the first address is NOT the router):

traceroute to www.yahoo.akadns.net (66.218.71.88), 30 hops max, 40
byte packets
 1  10.224.128.1 (10.224.128.1)  857.831 ms  2032.123 ms  2711.911 ms
 2  24-205-1-81.oc-stc.charterpipeline.net (24.205.1.81)  775.564 ms
9.070 ms  17.526 ms
 3  24-205-0-129.oc-stc.charterpipeline.net (24.205.0.129)  14.817 ms
13.828 ms  15.185 ms
 4  24-205-0-26.oc-stc.charterpipeline.net (24.205.0.26)  14.608 ms
13.989 ms  11.695 ms
 5  24-205-0-1.oc-stc.charterpipeline.net (24.205.0.1)  16.590 ms
12.787 ms  12.921 ms
[snip]

Now - I did a ping -f on 10.224.128.1 and got 100% packet loss, and
the same on 24.205.1.81 and got about a 50% packet loss.  Why is the
first address giving that much packet loss?  I suspect that the packet
loss at this level is what is causing me so much grief.

Also - as a side question, when I ping my router , I get 100% packet
loss.  Why is that?

Also - any recommendations as to what other diagnoses or info I should
give the cable modem guys?

Thanks for any help.

-Ed

 
 
 

Traceroute/ping help

Post by Stephan Korshol » Thu, 09 May 2002 07:06:42


Hi,

Quote:> Hi - currently have cable modem service with Charter.  Service has
> gotten really bad recently - very intermittent.
> ...
> I did a traceroute to
> www.yahoo.com (the first address is NOT the router):
> traceroute to www.yahoo.akadns.net (66.218.71.88), 30 hops max, 40
> byte packets
> 1  10.224.128.1 (10.224.128.1)  857.831 ms  2032.123 ms  2711.911 ms
> ...
> Now - I did a ping -f on 10.224.128.1 and got 100% packet loss

OK, first you did a traceroute and reached 10.224.128.1 - though with
a large delay - then afterward it was completely gone???

Maybe somebody switched off 10.224.128.1?

I've had a cable modem for nearly 3 years and I've had major problems
during two periods. The last time around the cable guy visited me
three times only to see that my modem worked fine (until he left the
building, when it failed again, again).

Finally I got lucky and it was failing permanently while he was
there. According to my experience the cable-modem technology is not
very reliable compared to i.e ADSL.

I'll suggest that you create a script that pings your logon server
every 5 minutes for a couple of days. This will give you a good
statistics measurement that will probably show that there is something
very wrong - depending on your supplier he may or may not take such a
measurement seriously.

Good luck (or switch to ADSL)!

- Stephan

 
 
 

Traceroute/ping help

Post by E » Thu, 09 May 2002 11:26:18



> OK, first you did a traceroute and reached 10.224.128.1 - though with
> a large delay - then afterward it was completely gone???

> Maybe somebody switched off 10.224.128.1?

Hi - no, not quite.  The whole point is that I can traceroute
www.yahoo.com and 10.224.128.1 will show up all the time.  However, if
I ping 10.224.128.1 directly, I always get 100% packet loss.  This is
what is confusing me.

-Ed

 
 
 

Traceroute/ping help

Post by Karl Heye » Thu, 09 May 2002 22:40:14




>> OK, first you did a traceroute and reached 10.224.128.1 - though with
>> a large delay - then afterward it was completely gone???

>> Maybe somebody switched off 10.224.128.1?

> Hi - no, not quite.  The whole point is that I can traceroute
> www.yahoo.com and 10.224.128.1 will show up all the time.  However, if
> I ping 10.224.128.1 directly, I always get 100% packet loss.  This is
> what is confusing me.

Not really difficult, traceroute sends packets (icmp/udp) to the
machines and icmp type 11 is sent back. ping sends icmp type 8 and
sends back type 0.  A firewall will be blocking type 0 and/or 8

karl.

 
 
 

1. need help ping/traceroute problems and more...

We're running linux with the 2.0.38 kernel, using a D-Link NE2000
compatible ISA network card.  We're connected to a Cisco 2500 series
router on a frame relay connection.  We're not running a firewall.

We can't ping or traceroute anywhere, not even the localhost.  It's like
all icmp traffic is being blocked.  Everything other than icmp
connections
to the internet and the localhost such as telnet, mail, etc, work just
fine.  I've tried upgrading the kernel and that didn't fix it.  We've
also
tried changing out the network card, and that didn't help either.  I
also
haven't been able to get tcpdump to work, so I'm not sure how to
diagnose
it from here.  We tried bringing the system down to single user mode
with
nothing but networking started, to see if perhaps something else was
interfering with it but no luck there either.

This just started happening one day a while back for no apparent reason.
No changes had been made to the system that we're aware of when it
started.

Please e-mail me any suggestions you might have.
Thanks so much,

Claus

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