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Re: About bridges

Robert Swindells wrote:
Staffan Thomén<>  wrote:
No takers for this? Can someone at least check that I'm not crazy?

Which bit of "this" ?

Your last message suggests to me that you have a working bridged network.

It works partially; DHCP replies don't seem to show up on the tap device so it
does not configure an address. I kept a tcpdump on the tap while running
dhcpcd and I can see dhcpcd retrying the sending to no avail.

Naturally I checked that my DHCP server sends the replies and it does. They
arrive on the real interface on the bridge under test (another simultaneous
tcpdump) but do not seem to pass through to the tap interface. As I
understand it, broadcast packets should be sent to every interface on the

While tcpdumping the tap device, I could see it sending the broadcast packets
for DHCP as well as multicast packets.

Additionally, even if I manually configure an address on the tap interface and
I can use it to connect using ssh, tcpdump on the tap device doesn't show the
unicast packets, which I don't think is right either.

What I did to test this was:

/etc/rc.d/dhcpcd stop, remove all addresses from all interfaces.

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

Watch dhcpcd properly configure IPv6 and finally add a zeroconf address as no
IPv4 broadcast reply from the server arrived.

In my initial test I used the wired wm0 interface, and it acts the same as with
the wireless.

It's entirely possible that I've fudged up something else in my network, I'd be
the first to say I don't know what I'm doing but I find that unlikely as the same
DHCP server servs a dozen or so clients on this network, some of which are
Xen domU:s that also live behind a bridge.


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