Strange network problems - pings to host are fine, pings from host fail

Strange network problems - pings to host are fine, pings from host fail

Post by David Brow » Wed, 03 Dec 2008 02:56:48



Sorry for the long post - I've tried to outline the symptoms of my
problem, and what I've tried to fix it.

I'm having some networking problems with a PC running an old version of
Red Hat (kernel 2.2).  The PC came with a machine we have bought
second-hand - as far as I know, everything was working before the
machine was moved to our company.

To keep things simple, we have the Red Hat machine connected to a
Windows XP machine that came with it, with only a simple switch in
between.  Each machine is set up with a fixed IP address on the same
network.

 From the XP machine, I can ping the Red Hat machine reliably and
quickly.  From the Red Hat machine, pings to the XP machine /generally/
fail - typically there are about 80%-90% failures.  Those pings that
don't fail, are fast (reply time about 1 ms).  On the XP machine, it's
easy to see the packet counters showing packets in and replies out.  On
the Red Hat machine, ifconfig shows similar packet rx and tx counts, and
zero error counts.

arping to the XP machine from the Red Hat machine is reliable and fast.

When we try a browser on the XP machine and address the web server on
the Red Hat host, there is generally a long pause (perhaps minutes),
then suddenly the page appears.

We have tried using another Linux box in place of the original XP
machine, with the same results from the Red Hat system.

We have tried replacing the cables and switch, with no effect - given
that arpings are working perfectly it's hard to see how it could be a
hardware problem.

I'm not very familiar with Red Hat or a 2.2 kernel (my experience is
mostly with Debian and related distros, and with 2.4 and 2.6 kernels).
But "ipchains -L" shows no firewalling (everything accepted), "ifconfig"
and "route -n" have the expected setup, and I could not stop anything
unexpected with "sysctrl".

One of my colleagues will try a different network card this evening.

Any ideas or tips would be much appreciated.  We've tried pretty much
every sensible idea we can think of, so I'm ready to listen to any crazy
or unlikely tricks.

mvh.,

David

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by Balwinder S Dheema » Wed, 03 Dec 2008 03:44:45



Quote:> Sorry for the long post - I've tried to outline the symptoms of my
> problem, and what I've tried to fix it.

> I'm having some networking problems with a PC running an old version of
> Red Hat (kernel 2.2).  The PC came with a machine we have bought
> second-hand - as far as I know, everything was working before the
> machine was moved to our company.

> To keep things simple, we have the Red Hat machine connected to a
> Windows XP machine that came with it, with only a simple switch in
> between.  Each machine is set up with a fixed IP address on the same
> network.

>  From the XP machine, I can ping the Red Hat machine reliably and
> quickly.  From the Red Hat machine, pings to the XP machine /generally/
> fail - typically there are about 80%-90% failures.  Those pings that
> don't fail, are fast (reply time about 1 ms).  On the XP machine, it's
> easy to see the packet counters showing packets in and replies out.  On
> the Red Hat machine, ifconfig shows similar packet rx and tx counts, and
> zero error counts.

> arping to the XP machine from the Red Hat machine is reliable and fast.

> When we try a browser on the XP machine and address the web server on
> the Red Hat host, there is generally a long pause (perhaps minutes),
> then suddenly the page appears.

> We have tried using another Linux box in place of the original XP
> machine, with the same results from the Red Hat system.

> We have tried replacing the cables and switch, with no effect - given
> that arpings are working perfectly it's hard to see how it could be a
> hardware problem.

> I'm not very familiar with Red Hat or a 2.2 kernel (my experience is
> mostly with Debian and related distros, and with 2.4 and 2.6 kernels).
> But "ipchains -L" shows no firewalling (everything accepted), "ifconfig"
> and "route -n" have the expected setup, and I could not stop anything
> unexpected with "sysctrl".

> One of my colleagues will try a different network card this evening.

> Any ideas or tips would be much appreciated.  We've tried pretty much
> every sensible idea we can think of, so I'm ready to listen to any crazy
> or unlikely tricks.

I think, you need to check DNS settings/entries on both of your XP as
well as RH machines; better automate all these and, or other such things
with the help of a DHCP server.

Moreover, try syncing your C:\WINDOWS\system32\drivers\etc\hosts file on
XP machine with the one /etc/hosts on you RH machine.

Or, better run a DNS server having zones for local/private network/segments.

Hope that helps,
--
Dr Balwinder S "bsd" Dheeman          Registered Linux User: #229709

Chandigarh, UT, 160062, India         Gentoo, Fedora, Debian/FreeBSD/XP
Home: http://cto.homelinux.net/~bsd/  Visit: http://counter.li.org/

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by Robert Harri » Wed, 03 Dec 2008 03:52:36



> Sorry for the long post - I've tried to outline the symptoms of my
> problem, and what I've tried to fix it.

> I'm having some networking problems with a PC running an old version of
> Red Hat (kernel 2.2).  The PC came with a machine we have bought
> second-hand - as far as I know, everything was working before the
> machine was moved to our company.

> To keep things simple, we have the Red Hat machine connected to a
> Windows XP machine that came with it, with only a simple switch in
> between.  Each machine is set up with a fixed IP address on the same
> network.

>  From the XP machine, I can ping the Red Hat machine reliably and
> quickly.  From the Red Hat machine, pings to the XP machine /generally/
> fail - typically there are about 80%-90% failures.  Those pings that
> don't fail, are fast (reply time about 1 ms).  On the XP machine, it's
> easy to see the packet counters showing packets in and replies out.  On
> the Red Hat machine, ifconfig shows similar packet rx and tx counts, and
> zero error counts.

> arping to the XP machine from the Red Hat machine is reliable and fast.

> When we try a browser on the XP machine and address the web server on
> the Red Hat host, there is generally a long pause (perhaps minutes),
> then suddenly the page appears.

> We have tried using another Linux box in place of the original XP
> machine, with the same results from the Red Hat system.

> We have tried replacing the cables and switch, with no effect - given
> that arpings are working perfectly it's hard to see how it could be a
> hardware problem.

> I'm not very familiar with Red Hat or a 2.2 kernel (my experience is
> mostly with Debian and related distros, and with 2.4 and 2.6 kernels).
> But "ipchains -L" shows no firewalling (everything accepted), "ifconfig"
> and "route -n" have the expected setup, and I could not stop anything
> unexpected with "sysctrl".

> One of my colleagues will try a different network card this evening.

> Any ideas or tips would be much appreciated.  We've tried pretty much
> every sensible idea we can think of, so I'm ready to listen to any crazy
> or unlikely tricks.

> mvh.,

> David

You may well have a hardware problem in your network. Try connecting
your Red Hat machine directly to your XP machine with a crossover cable
and try pinging again.

Robert

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by Tauno Voipi » Wed, 03 Dec 2008 04:17:29



> To keep things simple, we have the Red Hat machine connected to a
> Windows XP machine that came with it, with only a simple switch in
> between.  Each machine is set up with a fixed IP address on the same
> network.

>  From the XP machine, I can ping the Red Hat machine reliably and
> quickly.  From the Red Hat machine, pings to the XP machine /generally/
> fail - typically there are about 80%-90% failures.  Those pings that
> don't fail, are fast (reply time about 1 ms).  On the XP machine, it's
> easy to see the packet counters showing packets in and replies out.  On
> the Red Hat machine, ifconfig shows similar packet rx and tx counts, and
> zero error counts.

> Any ideas or tips would be much appreciated.  We've tried pretty much
> every sensible idea we can think of, so I'm ready to listen to any crazy
> or unlikely tricks.

> mvh.,

> David

Have you tried ping -n ?

--

Tauno Voipio
tauno voipio (at) iki fi

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by David Brow » Wed, 03 Dec 2008 05:38:38




>> Sorry for the long post - I've tried to outline the symptoms of my
>> problem, and what I've tried to fix it.

>> I'm having some networking problems with a PC running an old version
>> of Red Hat (kernel 2.2).  The PC came with a machine we have bought
>> second-hand - as far as I know, everything was working before the
>> machine was moved to our company.

>> To keep things simple, we have the Red Hat machine connected to a
>> Windows XP machine that came with it, with only a simple switch in
>> between.  Each machine is set up with a fixed IP address on the same
>> network.

>>  From the XP machine, I can ping the Red Hat machine reliably and
>> quickly.  From the Red Hat machine, pings to the XP machine
>> /generally/ fail - typically there are about 80%-90% failures.  Those
>> pings that don't fail, are fast (reply time about 1 ms).  On the XP
>> machine, it's easy to see the packet counters showing packets in and
>> replies out.  On the Red Hat machine, ifconfig shows similar packet rx
>> and tx counts, and zero error counts.

>> arping to the XP machine from the Red Hat machine is reliable and fast.

>> When we try a browser on the XP machine and address the web server on
>> the Red Hat host, there is generally a long pause (perhaps minutes),
>> then suddenly the page appears.

>> We have tried using another Linux box in place of the original XP
>> machine, with the same results from the Red Hat system.

>> We have tried replacing the cables and switch, with no effect - given
>> that arpings are working perfectly it's hard to see how it could be a
>> hardware problem.

>> I'm not very familiar with Red Hat or a 2.2 kernel (my experience is
>> mostly with Debian and related distros, and with 2.4 and 2.6 kernels).
>> But "ipchains -L" shows no firewalling (everything accepted),
>> "ifconfig" and "route -n" have the expected setup, and I could not
>> stop anything unexpected with "sysctrl".

>> One of my colleagues will try a different network card this evening.

>> Any ideas or tips would be much appreciated.  We've tried pretty much
>> every sensible idea we can think of, so I'm ready to listen to any
>> crazy or unlikely tricks.

> I think, you need to check DNS settings/entries on both of your XP as
> well as RH machines; better automate all these and, or other such things
> with the help of a DHCP server.

> Moreover, try syncing your C:\WINDOWS\system32\drivers\etc\hosts file on
> XP machine with the one /etc/hosts on you RH machine.

> Or, better run a DNS server having zones for local/private
> network/segments.

> Hope that helps,

It's not a DNS problem - I'm pinging by IP address.  I'm trying to keep
things as simple as possible until I know what's going wrong.

We have a DNS server on the router to which these machines will be
attached, once we've got this problem figured out.  And yes, I'll be
using the hosts files on both machines to make sure the naming is right.

Thanks for the ideas anyway.

mvh.,

David

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by David Brow » Wed, 03 Dec 2008 05:43:39




>> Sorry for the long post - I've tried to outline the symptoms of my
>> problem, and what I've tried to fix it.

>> I'm having some networking problems with a PC running an old version
>> of Red Hat (kernel 2.2).  The PC came with a machine we have bought
>> second-hand - as far as I know, everything was working before the
>> machine was moved to our company.

>> To keep things simple, we have the Red Hat machine connected to a
>> Windows XP machine that came with it, with only a simple switch in
>> between.  Each machine is set up with a fixed IP address on the same
>> network.

>>  From the XP machine, I can ping the Red Hat machine reliably and
>> quickly.  From the Red Hat machine, pings to the XP machine
>> /generally/ fail - typically there are about 80%-90% failures.  Those
>> pings that don't fail, are fast (reply time about 1 ms).  On the XP
>> machine, it's easy to see the packet counters showing packets in and
>> replies out.  On the Red Hat machine, ifconfig shows similar packet rx
>> and tx counts, and zero error counts.

>> arping to the XP machine from the Red Hat machine is reliable and fast.

>> When we try a browser on the XP machine and address the web server on
>> the Red Hat host, there is generally a long pause (perhaps minutes),
>> then suddenly the page appears.

>> We have tried using another Linux box in place of the original XP
>> machine, with the same results from the Red Hat system.

>> We have tried replacing the cables and switch, with no effect - given
>> that arpings are working perfectly it's hard to see how it could be a
>> hardware problem.

>> I'm not very familiar with Red Hat or a 2.2 kernel (my experience is
>> mostly with Debian and related distros, and with 2.4 and 2.6 kernels).
>> But "ipchains -L" shows no firewalling (everything accepted),
>> "ifconfig" and "route -n" have the expected setup, and I could not
>> stop anything unexpected with "sysctrl".

>> One of my colleagues will try a different network card this evening.

>> Any ideas or tips would be much appreciated.  We've tried pretty much
>> every sensible idea we can think of, so I'm ready to listen to any
>> crazy or unlikely tricks.

>> mvh.,

>> David
> You may well have a hardware problem in your network. Try connecting
> your Red Hat machine directly to your XP machine with a crossover cable
> and try pinging again.

We thought of that, but I couldn't find a crossover cable at the office
(we haven't needed crossover cables for a decade or so).  We have tried
connecting using only a modern switch, and also using an old 10 MBit
hub, as well as connecting them on the LAN side of a small router (a
LinkSys WRT54GL running openwrt).  There were absolutely no differences,
so I don't think the problem can be there.

If there is a hardware problem, it must lie with the network card on the
Red Hat machine, as everything else has been tested (different cables,
different target machines, etc.).  It's conceivable that the card has
come lose while transporting the machine to our offices, I suppose.
I'll know a little more in the morning (after my colleague has tried a
different network card).

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by David Brow » Wed, 03 Dec 2008 06:15:42




>> To keep things simple, we have the Red Hat machine connected to a
>> Windows XP machine that came with it, with only a simple switch in
>> between.  Each machine is set up with a fixed IP address on the same
>> network.

>>  From the XP machine, I can ping the Red Hat machine reliably and
>> quickly.  From the Red Hat machine, pings to the XP machine
>> /generally/ fail - typically there are about 80%-90% failures.  Those
>> pings that don't fail, are fast (reply time about 1 ms).  On the XP
>> machine, it's easy to see the packet counters showing packets in and
>> replies out.  On the Red Hat machine, ifconfig shows similar packet rx
>> and tx counts, and zero error counts.

>> Any ideas or tips would be much appreciated.  We've tried pretty much
>> every sensible idea we can think of, so I'm ready to listen to any
>> crazy or unlikely tricks.

>> mvh.,

>> David

> Have you tried ping -n ?

I'm already pinging by ip address, so "ping -n" should not make a
difference.  Or is it the case that with this setup (either Red Hat
specific, or kernel 2.2, or older versions of ping and the resolver
libraries), that ping without the "-n" will try to do a reverse DNS
lookup to find a name for the ip address I'm pinging?  I must admit that
I haven't worried too much about DNS so far, since I am sticking to IP
addresses first.  The DNS server specified on the Red Hat machine does
not exist in our network (it is a local address on the original user's
network), so perhaps ping is* when trying to resolve a name for
the address.  A similar thing may be happening with the web server
accessed by the client machine.  This is not a problem I've seen before
(I've seen other DNS issues, and also set up nodes and networks with no
DNS at all), but it may just be the problem.

I'll try out some fixes first thing in the morning when I'm back at the
office (firstly by putting the ip addresses I'm pinging in the hosts file).

Thanks for the hint!

mvh.,

David

 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by Allen McIntos » Wed, 03 Dec 2008 10:08:30




>> Have you tried ping -n ?
> I'm already pinging by ip address, so "ping -n" should not make a
> difference.  Or is it the case that with this setup (either Red Hat
> specific, or kernel 2.2, or older versions of ping and the resolver
> libraries), that ping without the "-n" will try to do a reverse DNS
> lookup to find a name for the ip address I'm pinging?

By default, ping tries reverse DNS on the source IP address of the
packet it gets back.
 
 
 

Strange network problems - pings to host are fine, pings from host fail

Post by David Brow » Wed, 03 Dec 2008 17:06:06





>>> Have you tried ping -n ?
>> I'm already pinging by ip address, so "ping -n" should not make a
>> difference.  Or is it the case that with this setup (either Red Hat
>> specific, or kernel 2.2, or older versions of ping and the resolver
>> libraries), that ping without the "-n" will try to do a reverse DNS
>> lookup to find a name for the ip address I'm pinging?

> By default, ping tries reverse DNS on the source IP address of the
> packet it gets back.

That was the problem.  A couple of lines in the hosts file (and correct
DNS setup once the system was connected to the rest of the network), and
everything worked perfectly.

Many thanks to those who replied on this thread - I've learned something
new, and fixed our problem.

mvh.,

David

 
 
 

1. Can't ping the host name or host IP address from host.

Hello there,
I have the unusual problem of not being able to ping the machines host name
or host IP address from the host.
I've checkout the network settings and I can't seem to find any problems.  I
am able to ping & telnet to the machine
from the network.  Seems quite strange.

Any help would be really appreciated.

thanks,

Owen.

Here is output from ifconfig


lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Bcast:127.255.255.255  Mask:255.0.0.0
          BROADCAST LOOPBACK  MTU:3584  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0

eth0      Link encap:Ethernet  HWaddr 00:60:08:83:28:08
          inet addr:10.0.0.100  Bcast:10.0.0.255  Mask:255.0.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:41411 errors:0 dropped:0 overruns:0 frame:0
          TX packets:259 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0
          Interrupt:3 Base address:0x300



PING penguin (10.0.0.100): 56 data bytes
ping: sendto: Network is unreachable
ping: wrote penguin 64 chars, ret=-1

--- penguin ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss


PING 10.0.0.100 (10.0.0.100): 56 data bytes
ping: sendto: Network is unreachable
ping: wrote 10.0.0.100 64 chars, ret=-1

--- 10.0.0.100 ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss

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