Re: Local Network Problem

Nils Kassube wrote:
Don Henson wrote:
Eberhard Roloff wrote:
Don Henson wrote:
To make a long background story short...

In restoring from a major system crash, I ended up with a
server/workstation, a workstation, and a laptop (wifi) that should
be talking to each other over Ethernet. The laptop will not respond
to a ping from anybody and the other two will respond to each
other's pings if I use the domain address. They will not respond if
I ping the corresponding IP address. This seems backwards to me but
that's the way it is. At one point, I had all three machines talking
but after rebooting all three, the problem returned. I've been
working on this for a couple of days and now I find myself
thoroughly confused. I have no idea which files and logs might be
useful. If you are interested in helping, let me know what data you
need and I'll post it forthwith. I'd really appreciate a little help
on this one.

Don Henson
on each one:

ifconfig eth0
cat /etc/hosts

then: Do you use a dhcp server for your machines? (For example, your
router could be acting as such a server)

do you use a firewall on all your machines or on specific machines?

What does a packet sniffer, ex. ethereal show on your laptop, when
you try to ping it from another machine.

If you are working with fixed ip addresses, what happes if you
connect only two machines via a crossover cable , i.e. leave out your
swith and anthing else in between.

kind regards
Eberhard
Per your request...

For Earth-svr
dhenson@Earth-svr:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:07:E9:9C:26:0B
inet addr:192.168.1.51 Bcast:192.168.1.255

dhenson@Earth-svr:~$ cat /etc/hosts
# 127.0.0.1 localhost

Please uncomment this entry, although it seems to be unrelated to your
problems.

Thanks. I must have looked at that line a hundred times and never
noticed that hashmark.

192.168.1.51 Earth-svr.site Earth-svr localhost

Localhost should be 127.0.0.1 not the address of an external interface. It
may work, but I think it is quite unusual.

One of my troubleshooting efforts. Changed back.

192.168.1.52 Venus-ws.site Venus-ws
192.168.1.53 Mars-laptop.site Mars-laptop

For Venus-ws

jhenson@Venus-desktop:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:15:F2:5B:9B:10
inet addr:192.168.1.52 Bcast:192.168.1.255

jhenson@Venus-desktop:~$ cat /etc/hosts
127.0.0.1 localhost
192.168.1.51 Earth-svr.site Earth-svr
192.168.1.52 Venus-ws.site Venus-ws
192.168.1.53 Mars-laptop.site Mars-laptop

For Mars-laptop

dhenson@Mars-laptop:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:19:B9:76:09:3C
inet addr:192.168.1.53 Bcast:192.168.1.255

wlan0 Link encap:Ethernet HWaddr 00:19:7E:62:59:16
inet addr:192.168.1.53 Bcast:192.168.1.255

Don't use two interfaces with the same IP address. That can't work. Please
note: An IP address defines an interface, not a machine. Probably this is
the reason why your laptop can't talk to anybody.

I named the eth0 interface 'Mars-wired' and assigned an ip address of
192.198.1.54.

dhenson@Mars-laptop:~$ cat /etc/hosts
127.0.0.1 localhost
192.168.1.51 Earth-svr.site Earth-svr
192.168.1.52 Venus-ws.site Venus-ws
192.168.1.53 Mars-laptop.site Mars-laptop.site

The original install used DHCP but I am tryng to switch to static.

My Linksys router/switch has a firewall. I use that and my machines
have their firewalls turned off.

I don't see an entry for your router in any of your /etc/hosts files. You
should add a line

192.168.1.1 router.site router

to each of the files (I assume it has the address 192.168.1.1). Otherwise
you can't talk to the internet.

Added

What is the output of the route command on your machines? It should look
like this:

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
default router.site 0.0.0.0 UG 0 0 0 eth0

The first line defines the local network, so you can talk to the other
local machines. These machines can be reached directly without a gateway.
The second line defines the rest of the world. To reach any non-local
machine the data should be sent to the gateway router.site.

dhenson@Mars-wired:~$ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0
wlan0
link-local * 255.255.0.0 U 1000 0 0 eth0
default router.site 0.0.0.0 UG 0 0 0
wlan0
default router.site 0.0.0.0 UG 0 0 0 eth0
dhenson@Mars-wired:~$

BTW: Why don't you want to use DHCP? It can make life so much easier. If
you just don't want to use the built-in DHCP server of the router you
could install a DHCP server e.g. on your Earth-svr machine.

I was having problems getting everything to work. Static addressing
*sounded* easier. If I wanted to change back, I would turn on the DHCP
server and change the entries in /etc/network/interfaces to dhcp instead
of static. Are there any other changes I should make?


Nils

I think I just discovered "THE BIG PROBLEM". When I restarted
networking, '/etc/init.d/networking restart', I got the following response:

dhenson@Mars-wired:~$ sudo /etc/init.d/networking restart
Password:
* Reconfiguring network interfaces... Error for wireless request "Set Encode" (8B2A) :
invalid argument "<my password>".
mount: can't get address for linux.site
mount: can't get address for linux.site
mount: can't get address for linux.site
mount: can't get address for linux.site
RTNETLINK answers: File exists
run-parts: /etc/network/if-up.d/avahi-autoipd exited with return code 2
mount: can't get address for linux.site
mount: can't get address for linux.site
mount: can't get address for linux.site
mount: can't get address for linux.site
[ OK ]
dhenson@Mars-wired:~$

I had seen this linux.site error message before but couldn't figure out
where it came from. linux.site was the original name for my server but
was changed to Earth-svr.site early on. Suddenly it hit me. When trying
to set up NFS, I added some (incorrect) lines to /etc/fstab. I checked
and they were still there. I removed those lines and restarted
networking. Only one hopefully minor error reported. This time I got:

dhenson@Mars-wired:~$ sudo /etc/init.d/networking restart
* Reconfiguring network interfaces...
Error for wireless request "Set Encode" (8B2A) :
invalid argument "<my password>".
RTNETLINK answers: File exists
run-parts: /etc/network/if-up.d/avahi-autoipd exited with return code 2
[ OK ]
dhenson@Mars-wired:~$

Now every machine can ping each other and I still have access to the
Internet. Thanks for your help.

Don Henson

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