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Re: About bridges



David Young wrote:
On Sun, May 30, 2021 at 01:21:17AM +0300, Staffan Thomén wrote:
ifconfig tap0 create up ifconfig bridge0 create up brconfig bridge0 add
iwn0 stp iwn0 add tap0 <wait until bridge settles into forwarding> <in
another terminal, start tcpdump -i tap0> dhcpcd -1 tap0

What mode is iwn0 in?  Access point?  Client?

You can add a wireless client interface to a bridge, but frames sent with
a different source MAC than the wireless NIC's MAC may be dropped by the
access point.  I guess it's possible that the source MAC will be
overwritten with your wireless NIC's MAC; then replies will carry the
wrong destination address.

The iwn0 device was a client here, connected using wpa_supplicant. The
wireless access point is not the dhcp server in the network.

As it is though, whether I use a wired or wireless interface the result is the
same.

I have to modify my statement though, it's not just broadcast packets that are
lost; when I tried using a wired interface (like I did when I first tried this
setup) broadcast packets did not arrive, but I couldn't get it to communicate
even if I set an address on the tap interface manually, so neither broadcast
nor unicast packets arrived (tcpdump of the tap showed multicast packets and
unicast packets to other hosts just like before though)

I am now wondering if I had addresses in my ARP table when I first tested it,
which helped it communicate with a static address set. Or just wasn't very
observant when I was doing my testing and some other interface had an
address configured.

Staffan


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