FreeBSD Bridge and ARP question/strangeness

Cole cole at opteqint.net
Thu Nov 20 02:25:56 PST 2008


Hi.

I have been playing with FreeBSD bridging in 7.0-Release. And was just
testing some things to see exactly how it worked and try a few things out. I
know that this isn't how the bridge is meant to be setup, but now im just
curious as to why the following is happening.

I have a box with a few interfaces, and i had setup rl0 with an ip address
and it could communicate/ping everything on the network fine, all the rest
of the other interfaces are unplugged and have no ip's assigned. Now if i go
ahead and create a bridge interface and then just add that single interface
with the ip assigned to it to the bridge, without assigning a new ip to the
bridge, i get some strange things happening. Every box on the network not
running FreeBSD is still able to ping and receive a reply from the box on
the ip it was using on the interface. However, no FreeBSD box is now able to
ping the box at all. In the arp listing, it shows any of the FreeBSD boxes
that are trying to ping it as "(incomplete)". But for every other box that
isn't FreeBSD it gets a full arp listing and all those boxes are still able
to communicate with the box fine.

So i was just wondering if theres a reason for this, or if anyone has any
idea or clues why this might be happening. If you want i can provide
whatever dumps you would need or anything like that.

Regards
/Cole



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