Bizarre RH 8 networking problem
 

Hi,

I am a bit of a Linux novice, have been running RH 7.2 for a while but haven't really had to get my hands that dirty with it.

Issue with networking 2 machines (through dedicated switch, no external connections, RH 8 and Win XP), ping works but only under the most bizarre circumstances. Boot both machines normally and attempt to ping each other and get 'Destination Host Unreachable' message from Linux and time out from XP. However fire up Ethereal on the Linux box, start capturing traffic from eth0 and everything works fine, pings in both direction. Stop the capture and the errors reappear!

What is ethereal doing as it is capturing traffic that isn't there normally?

Details:

Machine 1 RH8.0 - static IP Address

/etc/sysconfig/networking/profiles/default/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.5.255
IPADDR=192.168.5.1
NETMASK=255.255.255.0
NETWORK=192.168.5.0
ONBOOT=yes
USERCTL=no
PEERDNS=no
TYPE=Ethernet
HWADDR=00:40:f4:58:20:de

/etc/sysconfig/network

NETWORKING=yes
HOSTNAME=sccln01

/etc/modules.conf

alias parport_lowlevel parport_pc
alias scsi_hostadapter aic7xxx
alias eth0 natsemi
alias usb-controller usb-uhci

[root@sccln01 root]# lsmod
Module Size Used by Not tainted
ide-cd 33608 0 (autoclean)
cdrom 33696 0 (autoclean) [ide-cd]
soundcore 6532 0 (autoclean)
autofs 13348 0 (autoclean) (unused)
natsemi 18864 1
mousedev 5524 1
keybdev 2976 0 (unused)
hid 22244 0 (unused)
input 5888 0 [mousedev keybdev hid]
usb-uhci 26188 0 (unused)
usbcore 77024 1 [hid usb-uhci]
ext3 70368 6
jbd 52212 6 [ext3]
aic7xxx 137140 5
sd_mod 13552 10
scsi_mod 107144 2 [aic7xxx sd_mod]



Machine 2 Win XP Pro - static IP Address

C:\>ipconfig

Windows IP Configuration

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.5.7
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :


This has been driving me mad for the last 2 days – any help appreciated.

Thanks

John

It's not a duplex mismatch is it? Are both ends set to autonegotiate or have you configured the speed and duplex manually?

Do you have any ipchains rules defined by default? At some point RH began asking how you want your firewall to be config'd during install. If you specify medium or high, then you may be blocking the ping requests.

That wouldn't explain why the ethereal is allowing packets to come thru, unless it is setting eth0 to promiscuous mode. (different concept altogether).

Potential NIC Duplex \ Speed issues
 

Have not set anything up manually for either the RH8 network card or the XP one.

The netgear switch that I am using is showing both connections at 100mb and when I ping the lights flash on the switch for the correct ports. The speed that the cards are operating at shouldn’t be an issue should it?

Re duplex settings for the network cards – again haven’t set anything manually although I know that the XP machine is running full duplex, my impression is that with the switch I am using speed and duplex mode shouldn’t be an issues – the switch autonegotiates etc. Might be wrong though!

Is there anything specific that I can check to rule this out?

Is there a firewall at the bottom of this?
 

Does RH 8 use ipchains or tables, think it is the latter – concepts should be similar?

When I installed (should say reinstalled !) conciously set the security option to ‘No Firewall’ however the strange thing is that when I go into the RH desktop and run the graphical security applet it tells me that the security setting is High and won’t let me change it, weird!

Suspect that there might be some firewall issues at the bottom of this (that’s why I tried to reinstall with none). Have never played with firewalls, any clues re how I can analyse \ resolve?

Re: Is there a firewall at the bottom of this?
 

I have been using 7.3 and it had both installed. I just got my 8.0 up and running today, and I see that they have dropped ipchains.

run the following command on your running system;
This will tell you what rules are defined. You may want to move this post to the Linux-Security forum for better assistance on interpreting any rules that are defined.

If you just want to flush the table for troubleshooting, then use the -F option with no arguments.

HTH
Jeremiah

Hi Jeremiah,

Apologies for the tardiness in my reply – had to take the wife and kids away for the weekend.

Have run the command ‘iptables –L’ and get the following response:

‘Bash: iptables: command not found’

I guess from this that they aren’t running?

If so back to square one, maybe it is an issue with the hardware (Netgear FA-311), any other suggestions gratefully received.

Did you do this command as root? I tried to run the command as my user ID but got a similar message.

Jeremiah