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Re: About bridges

Robert Swindells <> writes:

> Staffan Thomén <> wrote:
>>brconfig bridge0 add wm1 stp wm1 add wm2 stp wm2 add wm3 stp wm3
>>This all works, packets flow and addresses are learned on all
>>interfaces, but ONLY if there is a cable with a link on wm1. It seems to
>>be that if there is no link on wm1 the interface (status: no carrier and
>>address shows <DETACHED>) gets disabled in the bridge, which kind of
>>sucks because then the host has no address and communication stops.
> [snip]
>>So how is this supposed to work? Can I force the interface with an
>>address to stay enabled somehow or is there a pseudo-device that I
>>haven't found that I should be using?
> My reading is that this is caused by revision 1.175 of if_bridge.c which
> explicitly changed bridge(4) to behave in this way.

I can see the point of considering an address detached if link is down
and it's from DHCP.  For static, I don't understand the reasoning.

bridges are a layer2 thing; they shouldn't care about the presence of IP

> I have been caught out by this change in a different way. I just use
> dhcpcd(8) to configure IPv6 and have static IPv4 addresses on everything
> on my LAN.
> When I add the upstream interface to a bridge this toggles the status
> on the interface and something in dhcpcd(8) or resolvconf(8) overwrites
> my /etc/resolve.conf with an empty one.

That seems like a different issue.  If you want dhcp processing to only
set resolv.conf when hearing on one particular interface, you should be
able to configure it.   But maybe I'm just not following.

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