CFT: new trunk(4)

Peter Jeremy peterjeremy at
Wed Apr 11 19:15:00 UTC 2007

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.
>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.

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.

BTW, you might like to study the fine print for whichever trunking
protocol you are using.  At least some of the proprietary protocols
are fairly dumb and just round-robin MAC addresses between the
physical links rather than dynamically sharing traffic across the
available links.  The former means that if most or all of your traffic
is for a single MAC address, you don't actually gain anything by
having multiple physical links.

Peter Jeremy
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