We have several FreeBSD 4.7 boxes that put automatically
all their interfaces into promiscuous mode during the
boot process. What should I do to prevent this from
happening ?

Our boxes are connected on a D-Link switch. We have noticed
a very weird behaviour from a few of these machines, I'll
try yo explain it :

Our switch has a standard MAC address aging value of 300 seconds.
When one MAC address expires on the switch, the next packet targeted
to this MAC address is broadcasted on all ports of the switch (because
the switch doesn't remember anymore on what port the target MAC address
is). That at least seems to be normal.

But each time an ethernet packet broadcasted as descrbibed above arrives
on the interfaces of our machines, these machines resend the packet to
the network, decrementing the TTL value bye one. I mean, these machines
are resending packets that are NOT targeted to them - neither the
destination MAC address OR the destination IP address of the packet
match the interface of the machine.

This happends only on machines with interfaces in promiscuous mode
AND with net.inet.ip.forwarding = 1.
There's your answer.  Any machine with forwarding turned on will resend
a packet that isn't destin for it.  That's by design.
It doesn't make much sense to me that you'd have a lot of machines with
forwarding turned on.  Usually only gateways use this.  Honestly, I
can't thing of any reason to have forwarding on if your machine only
has 1 IP address.

As several boxes have this problem, they resend packets to each others
very quickly, generating a flood on the network. This flood only stop
when all TTL of packets reach 0 or when the switch finally re-learn
on what port is located the interface with the target MAC address.

Does anybody have any clue about what this kind of problem may be ?
Turn forwarding of on all but your gateways.


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