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SubjectRe: Where do packets sent to 255.255.255.255 go?
25.08.2005 03:02, Daniel Brockman wrote/a écrit:
> Hi list,
>
> If I understand correctly, packets sent to the all-ones
> broadcast address only go out through a single interface.
Hello,

I have some blur memories about this kind of issue, so my answer my be
wrong on some points...

>
> My question is threefold:
>
> 1. Why doesn't Linux send 255.255.255.255 packages through
> all network interfaces? (I realize that this is
> probably not a Linux-specific question.)
IIRC, Linux 255.255.255.255 as a normal IP address. Therefore it will
follow the route for such an address and select the interface it is
associated (probably eth0 if you are on a LAN).

>
> 2. How does it choose which interface to send through?
> My first guess was that it just took the first Ethernet
> interface and used that for broadcasting. But playing
> around with nameif, this seems not to be the case.
cf 1

>
> 3. Can I set the default broadcast interface explicitly?
> For example, say I wanted broadcasts to go out over eth1
> by default, instead of over eth0. What if I wanted them
> to get sent through tap0?
Again, I'm not sure, but I think that you can force the interface by
adding a special route for IP 255.255.255.255 and with mask
255.255.255.255 to the interface you want.


[sniped]

Hope this help, even if my memory is a bit confused,
Eric

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