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Old 06-05-2005, 09:26 PM   #1
ses
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Registered: Jun 2005
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Swapping cables to eth0 & eth1 on the same machine still works. Why?


I seem to have a problem in my Redhat 7.1 network. I have 2 linux machines with 2 network cards of the same kind configured into each machine.

With the cables connected from eth0 of machine1 to eth0 of machine2, eth1 of machine1 to eth1 of machine2, I can perform ping to each other(naturally of couse).

However, if I connect eth0 of machine1 to eth1 of machine2, eth1 of machine1 to eth0 of machine2, I can STILL PERFORM ping to each other. This might seem like a good feature because there is no need to worry about connecting the wrong cable to the wrong card. But I have noticed that if one link is physically down, the other link would be down too even though it is still connected. With the same setup except one machine is now configured into Windows, I could not get both the machine to ping each other when the cables are connected wrongly.

If seems like it only occur when there are two linux machine connected to each other using dual ethernet would have this problem. Anyone encounter the same situation as me and any solution to disable this "feature" or any explanation?

Thanks!

p.s. I have just tried using a different type of network card and the problem still exist. The initial network cards that I was using is a 100baseFx(PCnet32 drivers) whereas the other network card that I am using is 100baseTx (EEpro100 drivers).
 
Old 06-06-2005, 07:25 AM   #2
huibert.alblas
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Registered: Jan 2004
Location: Duesseldorf /Germany
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Hmm,

this is not a problem as such,
but only a problem because you think it is.

Go and read http://www.faqs.org/docs/linux_network/
Linux Network Administrators Guide

You will find out that this behaviour is ok.

Maybe, depending on your exact setup, ip addresses, routing tabels, dns servers and gateway configuration you _might_ have a problem,
but you gave absolutly no info about these importand "details"
 
Old 06-07-2005, 01:31 AM   #3
ses
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Registered: Jun 2005
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Opps, sorry, cos I was expecting some confirmation if anyone experience the same problem as me and any answer to it? I tried looking up the faq and couldn't figure out why it is happening. Are you able to point out to me which section is it documented in?

Nevertheless, here are the information which I can provide...
Running ifconfig,
eth0 Link encap:Ethernet HWaddr 00:C0:F2:00:C5:B4
inet addr:148.88.88.208 Bcast:148.88.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:261 dropped:0 overruns:0 carrier:261
collisions:0 txqueuelen:100
Interrupt:15 Base address:0xc800

eth1 Link encap:Ethernet HWaddr 00:C0:F2:00:69:85
inet addr:158.88.88.208 Bcast:158.88.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:261 dropped:0 overruns:0 carrier:261
collisions:0 txqueuelen:100
Interrupt:15 Base address:0xa000

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:226 errors:0 dropped:0 overruns:0 frame:0
TX packets:226 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0


Running route -n,
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
158.88.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
148.88.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
148.189.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
 
  


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