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RE: [Xen-users] Xen's interface in promiscuous mode

To: <jean-baptiste.favre@xxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Xen's interface in promiscuous mode
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Tue, 24 Feb 2009 11:25:49 +1100
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Thread-index: AcmWB2fIE41V/IC1T4K1yfDNAOmfoQACUi0Q
Thread-topic: [Xen-users] Xen's interface in promiscuous mode
> Hello all,
> Playing with Xen on GNU/Debian Lenny, I just discovered that all my
> virtual network cards are in promiscuous mode by default.
> Changing that manually does not seems to change anything (that is,
> everything still works great).
> Is there any reason to have virtual network cards in promiscuous mode
> And where can I change this default behaviour ?

The physical network adapters in Dom0 will be in promiscuous mode if
they are joined to a bridge.

The virtual network adapters in DomU are in promiscuous modem because
(as of the version of Xen in Lenny) they don't support multicast, and so
the only way they can receive multicast packets is to be in promiscuous

As of 3.3.0 or thereabouts, there is a way for the frontend to tell the
backend which multicast packets it is interested in, so the behaviour
may be different there.


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