Re: bridged vlan interfaces

On 11/29/07 08:46, Jonathan Thibault wrote:
>> s = switch port with out vlan 3
>> S = switch port with vlan 3
>> i = interface on linux box with out vlan 3
>> I = interface on linux box with vlan 3
>> b = bridge on linux box with out in.3
>> B = bridge on linux box with in.3
> 
> sib = works
> siB = (invalid)
> sIb = works
> sIB = works
> Sib = works
> SiB = (invalid)
> SIb = works
> SIB = nowork :(

Hum.  Well we know a couple of things:
  1)  The Linux box with vlan 3 and in.3 in the bridge works as long as
the switch port does not have vlan 3 assigned.
  2)  The Linux box with vlan 3 and the switch port with vlan 3 works as
long as in.3 is not in the bridge.

This means that the problem is only when all three aspects are in play
at the same time:  switch port with vlan 3, the Linux box with vlan 3,
and in.3 being in the bridge.

> The current active configuration is pretty much like SIb (using a 
> plain switch) and it works.  Of course in.2 is on the bridge as my 
> entire set of customers is in that vlan.

*nod*

> I toyed with tcpdump a bit and got slightly surprising results:
> 
> 'tcpdump -n -i in.2' -> I see my customer's traffic.
> 'tcpdump -n -i in' -> I see my customer's traffic.

I can't say as I'm completely surprised by this.  The ethernet frame is
all that is different, so you would still be able to discern the traffic.

> 'tcpdump -n -i in.2 vlan 2' -> Nothing at all.  Obviously since in.2 
> is untagged traffic.
> 'tcpdump -n -i in vlan 2' -> Nothing at all.

I think you should see some traffic with your last test.

> Now that last case has me a bit perplexed...  Normally, the *tagged* 
> traffic would enter/leave the physical interface itself.  It's a bit 
> strange to me that both in and in.2 would show tcpdump only untagged 
> frames.  Would this have something to do with the fact that the 
> tigon3 driver/hardware has vlan support built-in?

Agreed.  I have had very good luck using low end Realtek 8139 NICs, you
might want to spend $5 - $25 and try one out.

> I also managed to dig out an ethernet hub (a lot harder task than I 
> thought) but haven't had the chance to take it to the datashed (5'x5' 
> datacenter? ;) and sniff the backbone trunk itself for those elusive 
> vlan tags.

*Chuckle*  Have fun with that.  I like the term "Data Shed".  :)

> Cisco equipment would likely provide better diagnostics tools in the 
> radios.  This is Motorola, networking is one of their very many 
> sidelines but it's hard to beat the actual radio performance for the 
> price.  I guess building so many cell phones pays off ;)

*nod*



Grant. . . .

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