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Old 02-02-2010, 08:31 AM   #1
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Logical interface filtering

Hi All,

I have created 2 logical eth interfaces (eth0:1, eth0:2) on my physical interface (eth0). It was my understanding that by assigning the logical interfaces to another network, only the traffic destined for that network would reach the logical interface.

As it turns out, a tcpdump on all three interfaces (eth0, eth0:1, eth0:2) now shows the same traffic regardless of the packet's destination network.

Is this normal behaviour for logical interfaces in linux? Is there a way to configure the kernel to forward only the appropriate traffic to the logical interfaces?

I'm using Ubuntu Server 9.04

Old 02-02-2010, 10:07 AM   #2
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tcpdump uses methods at a lower level than the IP level to capture packets. It typically puts the ethernet hardware into promiscuous mode, in order to trap all traffic. You cannot extrapolate anything about the behavior of the logical interfaces from the behavior of tcpdump.
--- rod.


filtering, logical

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