CFT: new trunk(4)

Ian FREISLICH ianf at
Thu Apr 12 05:39:09 UTC 2007

Peter Jeremy wrote:
> --HcAYCG3uE/tztfnV
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> On 2007-Apr-11 15:43:04 +0200, Ian FREISLICH <ianf at> wrote:
> >Andrew Thompson wrote:
> >> On Mon, Apr 02, 2007 at 11:17:29AM +0200, Ian FREISLICH wrote:
> >> > We're making extensive use of vlans to increase the number of
> >> > interfaces availabble to us using switches to break out gigE into
> >> > 100M interfaces.  The bandwidth problem we're having is to our
> >> > provider, a 100M connection, and we're looking at doing exactly
> >> > this.  However, it appears that this interface can't trunk vlan
> >> > interfaces.
> =2E..
> >No, I'm sure I want it the way I said.  I know it sounds wrong, but
> >I just don't have enough PCI-X slots to waste 2 on physical 100M
> >NICs for the uplink from the routers.
> Trunking is a way of combining multiple physical interfaces to increase
> the bandwidth.  Trunking multiple VLANs on a single interface doesn't
> make sense to me.

802.1q is VLAN tagging and trunking.  This interface is LACP - link
aggregation.  I really think that it makes no sense to be able to
aggregate some ethernet interfaces and not others.  I suppose some
pedant will tell me vlan interfaces are not ethernet.

> I believe that the appropriate configuration for you is to have a
> single VLAN within one of your GigE links for traffic to your
> provider.  Within the switch you assign that VLAN to multiple 100M
> ports which are then trunked to the provider.  This means that your
> switch needs to understand trunking but FreeBSD doesn't.

This is the configuration I'm going to be testing with our provider
this morning because FreeBSD can't do link aggregation on VLAN
interfaces.  I'm hoping that not having IP data available to the
switch will not prevent it from working in our scenario.


Ian Freislich

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