Local network hosts unreachable

This is being posted to linux-admin and to linux-net.
If either of these groups are inappropriate for this
posting, please let me know.

I am running Debian/GNU linux and I have a 2 box LAN.
Mareschal has the hardware modem in it, and so is used
as a gateway to the Internet. I do not use it for
anything else (it is running Woody/Stable). My box
that I use as my daily desktop machine is Xander
(running Sarge/Testing). The two boxes are connected
by a 4 port switch. For the past few days I have been
unable to communicate between the two boxes.

Neither machine can ping the other (100% packet loss).
Traceroute is also unable to find a path from either
machine to the other. Ssh fails with an error saying
'no route to host.' This last error makes me feel
that something has been messed up with my kernel
routing tables, but they look OK to me and I have not
been able to correct the problem by making changes
there.

I do not see any obvious (to me) problems when the
systems are booting. Below are listings of
/etc/hosts, /etc/networks, as well as the output of
ifconfig and route for each of the machines.

If anyone can give me a clue what might be wrong I
would greatly appreciate it. Using a lousy web
interface to my e-mail from a Windows laptop is gettin
old very fast.

Here are the files and outputs:

Desktop box (xander):

/etc/hosts
127.0.0.1 local.net xander localhost
loopback
192.168.0.1 mareschal
192.168.0.2 alexander
192.168.0.3 xander

# The following lines are desirable for IPv6 capable
hosts
# (added automatically by netbase upgrade)

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts


/etc/networks
localnet 192.168.0.0


/sbin/ifconfig
eth0 Link encap:Ethernet HWaddr
00:11:5B:1B:8F:1F
inet addr:192.168.0.3 Bcast:192.168.0.255
Mask:255.255.255.0
inet6 addr: fe80::211:5bff:fe1b:8f1f/64
Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500
Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
frame:0
TX packets:534 errors:0 dropped:0 overruns:0
carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:22764 (22.2
KiB)
Interrupt:19 Base address:0xe400

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:230 errors:0 dropped:0 overruns:0
frame:0
TX packets:230 errors:0 dropped:0 overruns:0
carrier:0
collisions:0 txqueuelen:0
RX bytes:19436 (18.9 KiB) TX bytes:19436
(18.9 KiB)



/sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags
Metric Ref Use Iface
local.net * 255.255.255.255 UH
0 0 0 lo
localnet * 255.255.255.0 U
0 0 0 eth0
default mareschal 0.0.0.0 UG
0 0 0 eth0


Gateway box (mareschal):

/etc/hosts
127.0.0.1 local.net mareschal
localhost loopback
192.168.0.1 mareschal
192.168.0.2 alexander
192.168.0.3 xander

# The following lines are desirable for IPv6 capable
hosts
# (added automatically by netbase upgrade)

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts


/etc/networks
localnet 127.0.0.0


/sbin/ifconfig
eth0 Link encap:Ethernet HWaddr
00:40:05:73:C8:11
inet addr:192.168.0.1 Bcast:192.168.0.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500
Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
frame:0
TX packets:3 errors:0 dropped:0 overruns:0
carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:180 (180.0 b)
Interrupt:10 Base address:0x300

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:3924 Metric:1
RX packets:18 errors:0 dropped:0 overruns:0
frame:0
TX packets:18 errors:0 dropped:0 overruns:0
carrier:0
collisions:0 txqueuelen:0
RX bytes:1784 (1.7 KiB) TX bytes:1784 (1.7
KiB)



/sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags
Metric Ref Use Iface
127.0.0.1 * 255.255.255.255 UH
0 0 0 lo
192.168.0.0 * 255.255.255.0 U
0 0 0 eth0


Marc Shapiro


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Re: Local network hosts unreachable

Just wondering,

Did your setup ever work? If yes, does your 4
port switch have one of these buttons to select
Uplink on/off? If yes, is it in the correct
position?

I have had this problem several times, and the
cause has been someone cleaning up boxes and cables
and accidentally depressing this button and
changing its position.

Gerardo


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Re: Local network hosts unreachable

> --- gerardo juarez-mondragon
> wrote:
>
> > Just wondering,
> >
> > Did your setup ever work?

Yes. Everything worked fine until about a week ago.

> If yes, does your 4
> port switch have one of these buttons to select
> Uplink on/off? If yes, is it in the correct
> position?

Nothing is using the uplink/5th port, so it really
does not matter which position it is in.

Any help in gettin this to work will be greatly
appreciated. I am currently reduced to reading e-mail
and web-browsing on a Windows laptop with a 'g' key
that sometimes works and a broken hinge that could
fall off at any time.

Here is what information I have gathered, or been
asked for by others attempting to help me solve this
problem:

I am able to 'ping localhost' from either box.

I am unable to ping my gateway box from the desktop,
or ping the desktop from the gateway.

When I attempt a ping from either box to the other,
both sets of lights on the switch blink, suggesting
that data is going through the switch, both NICs and
both cables. The lights on the switch correctly
show 100Mb/sec full-duplex connections from both
machines. I have already changed the NIC on the
gateway machine in an attempt to solve this. The
desktop machine has a built in NIC and is only a few
months old.

Everything worked fine until about a week ago.

----------------------------------

On the desktop box (xander -- 192.168.0.3):

/etc/network/interfaces:

# /etc/network/interfaces -- configuration file for
ifup(8), ifdown(8)
# The loopback interface
auto lo
iface lo inet loopback
# The first network card - this entry was created
during the Debian installation
# (network, broadcast and gateway are optional)
auto eth0
iface eth0 inet static
address 192.168.0.3
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255

--------------------

output of ifconfig:

eth0 Link encap:Ethernet HWaddr
00:11:5B:1B:8F:1F
inet addr:192.168.0.3 Bcast:192.168.0.255

Mask:255.255.255.0
inet6 addr: fe80::211:5bff:fe1b:8f1f/64
Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500
Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
frame:0
TX packets:223 errors:0 dropped:0
overruns:0
carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:9534 (9.3
KiB)
Interrupt:19 Base address:0xe400
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:193 errors:0 dropped:0
overruns:0
frame:0
TX packets:193 errors:0 dropped:0
overruns:0
carrier:0
collisions:0 txqueuelen:0
RX bytes:72672 (70.9 KiB) TX bytes:72672
(70.9 KiB)

---------------------

/etc/hosts:

127.0.0.1 local.net xander localhost
loopback
192.168.0.1mareschal
192.168.0.2alexander
192.168.0.3xander
# The following lines are desirable for IPv6 capable
hosts
# (added automatically by netbase upgrade)
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

--------------------

/etc/networks:

localnet 192.168.0.0

--------------------

output of mii-tool:

eth0: negotiated 100baseTx-FD, link ok

--------------------------------------------

On the gateway box (mareschal -- 192.168.0.1):

/etc/network/interfaces:

# Used by ifup(8) and ifdown(8). See the
interfaces(5)
manpage or
# /usr/share/doc/netbase/examples for more
information.
#
iface lo inet loopback
iface ppp0 inet ppp
iface eth0 inet static
address 192.168.0.1
netmask 225.225.225.0
broadcast 192.168.0.225
network 192.168.0.0
up route add default ppp0
down route del ppp0

-----------------

output of ifconfig:

eth0 Link encap:Ethernet HWaddr
00:12:17:54:0D:EF
inet addr:192.168.0.1 Bcast:192.168.0.255

Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500
Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
frame:0
TX packets:48 errors:0 dropped:0
overruns:0
carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:2016 (1.9
KiB)
Interrupt:11 Base address:0x2400
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:67 errors:0 dropped:0
overruns:0
frame:0
TX packets:67 errors:0 dropped:0
overruns:0
carrier:0
collisions:0 txqueuelen:0
RX bytes:7028 (6.8 KiB) TX bytes:7028
(6.8
KiB)

----------------------

/etc/hosts:

127.0.0.1 local.net mareschal
localhost loopback
92.168.0.1mareschal
192.168.0.2alexander
192.168.0.3xander
# The following lines are desirable for IPv6 capable
hosts
# (added automatically by netbase upgrade)
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

----------------------

/etc/networks:

localnet 127.0.0.0

-----------------------

output of mii-tool:

eth0: negotiated 100baseTx-FD flow-control, link ok

------------------------------------------------

Marc


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Re: Local network hosts unreachable

Hi, Marc:

I believe your problem is a routing problem.

(without automatic word wrap in your email application)

I'd like to see the output of
route -n
from each machine.


A 'crossover' cable between the interfaces could help
rule out problems with the hub.

However, your original message's 'error' indicated a routing problem
and not a cable or hardware problem.

HTH, Chuck

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Re: Local network hosts unreachable

On Tue, 2005-05-03 at 03:00, chuck gelm wrote:
> Hi, Marc:
>
> I believe your problem is a routing problem.
>
> (without automatic word wrap in your email application)
>
> I'd like to see the output of
> route -n
> from each machine.
>
>
> A 'crossover' cable between the interfaces could help
> rule out problems with the hub.
>
> However, your original message's 'error' indicated a routing problem
> and not a cable or hardware problem.


And please also the output of
iptables -L


Andy


> HTH, Chuck
>
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Re: Local network hosts unreachable

--- Andrew Kelly wrote:

> On Tue, 2005-05-03 at 03:00, chuck gelm wrote:
> > Hi, Marc:
> >
> > I believe your problem is a routing problem.
> >
> > (without automatic word wrap in your email
> application)
> >
> > I'd like to see the output of
> > route -n
> > from each machine.
> >
> >
> > A 'crossover' cable between the interfaces could
> help
> > rule out problems with the hub.
> >
> > However, your original message's 'error'
> indicated a routing problem
> > and not a cable or hardware problem.
>
>
> And please also the output of
> iptables -L

I tried a crossover cable, with the same results, but
I am not convinced that it is working, either. This
evening I am going to try and see if I can get it (and
my switch) tested.

desktop box (192.168.0.3):

route -n:

Kernel IP routing table
Destination Gateway Genmask Flags
Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U
0 0 0 eth0
0.0.0.0 192.168.0.1 0.0.0.0 UG
0 0 0 eth0


gateway box (192.168.0.1):

route -n:

Kernel IP routing table
Destination Gateway Genmask Flags
Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U
0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U
0 0 0 eth0


I have removed iptables from the desktop box in an
effort to eliminate possible problems and I upgraded
the gateway box from a 2.2.xx to a 2.4.xx kernel and
have not yet installed iptables (to replace the
ipchains that had been running there) so there is
currently no firewall running on either box. (No need
for one until I can get this resolved.)

I appoloize for the word wrap. I am stuck using my
laptop (Windows) and a webmail gateway (Yahoo) until I
can get this fixed and have my desktop box back on the
Net. The automatic wrap seems to be a Yahoo Mail
thing.

Marc

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Re: Local network hosts unreachable

Marc Shapiro wrote:

> I tried a crossover cable, with the same results, but
> I am not convinced that it is working, either. This
> evening I am going to try and see if I can get it (and
> my switch) tested.

I suggest running tcpdump (with the -n switch) on both boxes then try
pinging each from the other. That will show whether anything is
getting through.

More generally, any time that you have a networking problem which
can't be resolved by trial-and-error within a couple of minutes, run a
packet sniffer and watch what is actually going across the wire.

--
Glynn Clements
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Re: Local network hosts unreachable

Your gateway machine routing table is, according
to your initial message:

/sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags
Metric Ref Use Iface
127.0.0.1 * 255.255.255.255 UH
0 0 0 lo
192.168.0.0 * 255.255.255.0 U
0 0 0 eth0


Is this complete? How do you reach the Internet?
The 'default' route should appear shouldn't it?

Gerardo


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