[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: Nasty little network problem



Ed Greshko <Ed Greshko greshko com> writes:

>> >   BROADCAST=192.168.0.255
>>                      ^^^^
>>                      ^^^^
>> 
>> Is this a typo or how it is really configured??
>
> If you look at the ifconfig output above you can conclude that this is
> how it is configured....incorrectly configured of course.  :-)

It wasn't a typo and infact the error existed on 2 machines on that
hub.  However it doesn't appear to have been significant.  Both have
now been corrected and ran `service network restart' on both machines.

So to summarize quickly:  4 machines on 1 hub all in 192.168.1.0
network.  All with broadcast set correctly.  All closely examimed for
other errors like having network set to 192.168.0.0 or something.  
I also found one that had that error.

Now after a close examination I believe all have correct settings.
Further 3 of four were able to talk to each other even with the
errors.  M2 could not and still M2 cannot.

Now here is some more info that really confuses me.
Unplug M1 and M2 ethernet cables from hub1.  Plug them into hub2
which is not connected to anything else.  Now M1 and M2 can talk to
each other.  (With no further network changes).

Plug them back into hub1 and they can't even with switching around
port holes and cables.   One might think a switch/hub would act like
that but it isn't supposed to.   Further, 3 of the machines on hub1
can all talk to each other.

Again I emphasis that I have switched port holes and cables around
several times.  Tested by unplugging and reconnecting to hub2, seeing
the results described above.

I've collected a set of data from the problem machine.  Wrote it to
floppy and insert it here.

But to describe the setup only in part for posters ease in seeing the
setup:       
                    INTERNET
                        |
                 (MORE ROUTERS and cable modem)
                        |
    M5 (rh7.1) eth1 is 192.168.1.6 eth0 is 192.168.0.5 

                        |
                        |
    ======================  HUB1  =====================
    |            |             |                   |
192.168.1.7  192.168.1.5   192.168.10         192.168.1.11
   M1         M2            M3                   M4

                ==== HUB2 ==== (not in use here)

Pulling M1 and M2 then reconnect to hub2 (and nothing else) and the
problem on M2 disappears.  It can talk to M1.  Very puzzling.

====================================

cat /etc/sysconfig/network:
NETWORKING=yes
HOSTNAME=hgp.local.lan
GATEWAY=192.168.1.6
-- 

cat /etc/sysconfig/network-scripts/*eth0:
DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.1.255
IPADDR=192.168.1.5
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
--

# ping 192.168.1.7
PING 192.168.1.7 (192.168.1.7) from 192.168.1.5 : 56(84) bytes of data.
>From 192.168.1.5 icmp_seq=1 Destination Host Unreachable
>From 192.168.1.5 icmp_seq=2 Destination Host Unreachable
>From 192.168.1.5 icmp_seq=3 Destination Host Unreachable
-- 

tcpdump -ieth0 (done while a ping as above is running):
eth0: Setting promiscuous mode.
tcpdump: listening on eth0
21:44:27.168895 arp who-has reader.local.lan tell hgp.local.lan
21:44:28.168470 arp who-has reader.local.lan tell hgp.local.lan
21:44:29.168464 arp who-has reader.local.lan tell hgp.local.lan
-- 

iptables -nL
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
-- 

ifconfig -a:

eth0      Link encap:Ethernet  HWaddr 00:04:75:AB:F2:33  
          inet addr:192.168.1.5  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:923 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1118 errors:0 dropped:0 overruns:0 carrier:36
          collisions:0 txqueuelen:100 
          RX bytes:58289 (56.9 Kb)  TX bytes:70652 (68.9 Kb)
          Interrupt:10 Base address:0x3000 

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:239 errors:0 dropped:0 overruns:0 frame:0
          TX packets:239 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:23900 (23.3 Kb)  TX bytes:23900 (23.3 Kb)
-- 

root # traceroute 192.168.1.6
traceroute to 192.168.1.6 (192.168.1.6), 30 hops max, 38 byte packets
 1  hgp (192.168.1.5)  2998.734 ms !H  2999.473 ms !H  2999.924 ms !H

root # traceroute 192.168.1.7
traceroute to 192.168.1.7 (192.168.1.7), 30 hops max, 38 byte packets
 1  hgp (192.168.1.5)  2998.647 ms !H  2999.482 ms !H  2999.916 ms !H






[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]