[Techtalk] Help!

[bsweeney]

Samantha wrote:

>Please forgive the cross posting I am desperate and
>trying to cover all bases at once.
>
No problem!  

>
>
>Today I ran RH's up2date program in order to take care
>of the security alert they emailed me about. Stayed
>logged in all day. When I logged out of Linux tonight
>and went over to the windows side of the box. When I
>rebooted Grub offered me 2 versions of Linux (2.4.7-10
>& 2.4.9-31) I assumed that the latter was the newer
>version and booted that one. The first thing that
>happened was I got a sound server error (cpu overload,
>aborting) which is fine because I have an integrated
>sound card that is not supported yet, then KNotify
>crashed. Hmmmm. okay close that app. 
>
I've had problems with this as well, though it seems to "go away" after 
a few reboots.  Haven't had time to really troubleshoot it unfortunately.

>Then I find that
>I am not connected to the net (I have DSL) even though
>I was and still am on the windows side. OK, reboot.
>Boot into the old version...no sound server error.
>Good sign or so I thought. Still no internet
>connection! Does anyone have an idea of why this is
>happening??
>
First question: Is it plugged in?  This may seem silly, but trust me 
asking this question could've saved me much heartache in many 
circumstances.  Check the cabling all around.  Do you have a link light 
on your NIC and your DSL router?  If not, look no further!  Try swapping 
cables, etc.  I know, the odds of a hardware problem developing just as 
you updated the kernel are slim.  Yet, that always seems to be when I 
find mine ;-)

If that doesn't work, I know RedHat did released an update for their 
init scripts to fix a problem aquiring/refreshing IP addresses.  I 
believe it was only for systems whos ip changes often (like my laptop, 
jumping from home lan to work lan), but I'm not sure.  In any case, the 
update didn't fix the issue for me.  The only thing that did was to 
issue a pump command manually.

So, as I believe someone else suggested, type an ifconfig -a command and 
see what the status of your network interfaces is.  If the network 
interface does not show up when you run ifconfig -a (ie, you don't see 
anything besides the "lo" interface), things get a bit more interesting 
as for whatever reason you're nic card isn't being recognized.  But I 
doubt that's it; if it is, post again. 

If it is there, try executing the command "pump -i <interface>" where 
interface is the name of your network interface (most likely eth0, 
though it could be eth1, eth2 etc if you have more than one network card 
in your system; it's NOT 'lo' though).  At that point, recheck your 
network interfaces, but this time just type ifconfig without the -a. 
 That'll show only the interfaces which are "up", along with ip, 
netmask, broadcast info, etc.  If you see your interface there with an 
ip address, and you still can't get network activity, try narrowing down 
the issue.  Ping an ip address on the net to see if it's a general 
networking failure or just a DNS issue; 216.239.51.101 and 
216.239.33.101are google ip addresses, and should respond.  Type "ping 
<ip>" to ping those hosts.  If that works, then type "ping 
www.google.com".  If THAT works, then general networking and DNS are 
working!  At that point, any inability to surf the web, check email, 
etc, would most likely be an application issue.  If pinging the ip 
addresses works, but pinging the names doesn't, check your 
/etc/resolv.conf file.  There will be listed your current nameservers. 
 Try pinging their ip addresses; do they respond?  If not, you've got 
issues contacting your name server.  Try calling your ISP to let them know.

If pinging the google ip addresses failed, type "netstat -rn" to get a 
list of your systems' routing information.  It should look something 
like this:

Kernel IP routing table
Destination            Gateway         Genmask         Flags   MSS 
Window  irtt Iface
<your-network>    0.0.0.0             <your-netmask>U        40     
 0              0   eth0
127.0.0.0                0.0.0.0             255.0.0.0           
U        40      0              0   lo
0.0.0.0                    <gateway-ip>   0.0.0.0            UG       40 
     0              0    eth0

The first line tells linux to address any systems on your subnet locally 
via eth0 (or whatever the name of your network interface is), sending 
information directly to them.  The second line tells your system to 
address itself via the loopback interface.  The third line tells your 
system to send any information not destined for one of the first two 
through your default gateway, whos ip address will be <gateway-ip> . 
 Try pinging this ip address.   If you can't, but you're sure you have a 
linklight, I'm not entirely sure where you should go from there. 
 Perhaps replace the nic?  If you have no line like the third line above 
in your routing table that has a destination of 0.0.0.0 with the flags 
"UG", then for whatever reason you didn't get routing information from 
your dhcp server.  Try '/etc/rc.d/init.d/network restart', and if that 
doesn't work, 'pump -i <interface>' again.   If again you get an ip 
address but not a router, your ISP may be having issues.  

As a final general troubleshooting note, try checking your log files for 
strangeness.  Use grep on /var/log/messages and /var/log/boot.log ("grep 
-i '<words-your-looking-for>' <filename>"; check out man grep for more 
info or ask here!)  Words I usually search for when troubleshooting an 
unknown problem include fail, error, panic, unable, timed out; in this 
case I would add dhcp to that list.

One last thing that just occured to me: are you running a firewall on 
this machine? I doubt that would be the problem, but just in case run 
'/etc/rc.d/init.d/ipchains status' and see if you've got a bunch of 
firewall rules, lines with ACCEPT and/or REJECT in front.  As temporary 
troubleshooting measure, if you are running the firewall, issue 
'/etc/rc.d/init.d/ipchains stop' to turn it off and see if your network 
returns.  If so, let us know and we can try troubleshooting the firewall 
config.

Hope something in that long ramble helps!

-Brian