Ping fails despite apparently good hardware and configuration

Issue:

My Redhat Linux 8 computer cannot communicate with other
computers on my LAN.


Key facts:


1. THERE IS NOTHING WRONG WITH THE HARDWARE

If I put in a Linux bootable CD and boot the basic Linux using the
same IP address and subnet mask I use when booting full Linux from
the hard drive, the computer communicates with the other two computers
on my LAN with no problem. Further, it worked fine when it was a
Windows 9x device.



2. IT'S NOT AN ADDRESS OR SUBNET MASK ISSUE

Per the above, I use the same address and subnet mask on the bootable
CD as the full PC, so it can't be that.



3. THE IFCONFIG RETURNS THE FOLLOWING

eth0 Link encap:Ethernet HWaddr 00:50:DA:6D:CF:39
inet addr:192.168.123.10 Bcast:192.168.123.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:67 errors:0 dropped:0 overruns:0 frame:0
TX packets:139 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:9125 (8.9 Kb) TX bytes:9252 (9.0 Kb)
Interrupt:10 Base address:0xd800

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:332 errors:0 dropped:0 overruns:0 frame:0
TX packets:332 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:27288 (26.6 Kb) TX bytes:27288 (26.6 Kb)

This looks quite normal to me. Also, it looks the same as what I
get from the ifconfig command when I'm on the bootable CD which works.



4. MY ETC/HOSTS FILE IS

127.0.0.1 localhost.localdomain localhost
192.168.123.10 pc99.localdomain pc99
192.168.123.11 pc03.localdomain pc03
192.168.123.12 lt03.localdomain lt03



5. YET, PING RETURNS THE FOLLOWING

PING pc03.localdomain (192.168.123.11) from 192.168.123.10 : 56(84) bytes of
data.
From pc99.localdomain (192.168.123.10) icmp_seq=1 Destination Host
Unreachable
From pc99.localdomain (192.168.123.10) icmp_seq=2 Destination Host
Unreachable
From pc99.localdomain (192.168.123.10) icmp_seq=3 Destination Host
Unreachable
From pc99.localdomain (192.168.123.10) icmp_seq=4 Destination Host
Unreachable
From pc99.localdomain (192.168.123.10) icmp_seq=5 Destination Host
Unreachable

--- pc03.localdomain ping statistics ---
5 packets transmitted, 0 received, +5 errors, 100% loss, time 4026ms, pipe 3



6. OTHER DEVICES CANNOT PING THE LINUX DEVICE

On my LAN are two Windows XP machines which communicate with each other just
fine, but neither of them can ping the Linux device.



Any assistance is greatly appreciated!

James

In article <bf9gig$fuq$1@bob.news.rcn.net>, James Madison wrote:
> My Redhat Linux 8 computer cannot communicate with other
> computers on my LAN.

Probably yet another one of the millions of firewall issues. You said
"yes" when you were asked in the setup if you wanted a firewall, right?

> 1. THERE IS NOTHING WRONG WITH THE HARDWARE
> 2. IT'S NOT AN ADDRESS OR SUBNET MASK ISSUE
> 3. THE IFCONFIG RETURNS THE FOLLOWING
>
> eth0 Link encap:Ethernet HWaddr 00:50:DA:6D:CF:39
> inet addr:192.168.123.10 Bcast:192.168.123.255 Mask:255.255.255.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:67 errors:0 dropped:0 overruns:0 frame:0
> TX packets:139 errors:0 dropped:0 overruns:0 carrier:0

Packets are being received and transmitted. What does "/sbin/route -n"
say?

> 4. MY ETC/HOSTS FILE IS
> 5. YET, PING RETURNS THE FOLLOWING

You can ping OUT without problems, right?

> 6. OTHER DEVICES CANNOT PING THE LINUX DEVICE
>
> Any assistance is greatly appreciated!

"service iptables stop" and ping away. "man chkconfig" to make the
firewall go away. http://www.netfilter.org/ and see Rusty's Unreliable
Guides if you want to know how to make a useful firewall.
--
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