> Naw... that's not how you'd configure it. Lets say we have this:
>
> ---------- ---------- ---------- ---------
> | A |--------| B |--------| C |---------| D |
> ---------- ---------- ---------- ---------
>
> Now... if a packet leaves A on vlan 57, it will arrive at B marked
> with vlan 57. If the BC link is the "same" trunk, the packet might
> continue on vlan 57. Now if the CD link is a different "trunk" (and
> this is just an organizational issue), then the packet might be
> rewritten to have vlan 225 on it --- and would make that leg of the
> journey with vlan 225.
hmm... my understanding was (but i might be wrong) that _normally_
end hosts do not tag packets, the tag insertion/removal (this is
what i meant by encapsulation/decapsulation in my previous email)
is done by the VLAN bridge when such packets go through a trunk
interface (i.e. the link connected to that interface supports
traffic for multiple independent VLANs).
My point is that you don't know what happens to the traffic on
that link -- your network admin could decide to further aggregate
such traffic by forwarding it into a "normal" port of another
VLAN bridge, which then does the tagging again.
Agreed, this is not how you'd configure it, but as you say
> ........................ The possibilites simply explode ... not the
> In short, vlan tags are not like GRE (which might be the confusion)
> ... they are simply part of the ethernet header.
not fully sure about that. How could you possibly prevent a frame
from being untagged multiple times if the frame has an appropriate
bit pattern ?
cheers
luigi
-----------------------------------+-------------------------------------
Luigi RIZZO, [EMAIL PROTECTED] . Dip. di Ing. dell'Informazione
http://www.iet.unipi.it/~luigi/ . Universita` di Pisa
TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy)
Mobile +39-347-0373137
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