Alex Zeffertt wrote: > On Sat, 23 Jul 2005 20:59:11 -0700 > Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote: > > >>Alex Zeffertt wrote: >> >> >>>I see your point about leaving the vlan tag in the name but I don't think it is valid in this >>>particular scenario. Although each frame sent to the CPU over the MII has a tag, the frame does >>>not have a tag when it enters the switch via one of the other ports. Similarly, when the CPU >>>sends a frame over the MII it is tagged, but the switch removes the tag before sending it out. >>>Therefore the tags are used solely on the MII bus as a way of indicating on which port the frame >>>was received/to which port it should be sent. This is an implementation detail that I want to >>>hide and make it look like I've just got 10 NICs. >> >>So what happens when the user configures a VLAN on this 'ethernet' port? >> > > > Ben, > > Very good question. In principle you just get double tagged frames being sent to and fro over the > MII port, and single tagged frames being sent to and fro over the switch fabric's other ports. > However, in reality it's going to be fiddly to get this to work.... > > Firstly (and most obviously) you need to choose a switch fabric which can do jumbo frames (i.e. > > 1522 bytes). > > Secondly you need to be able to make the switch fabric ignore any vlan tags on it's non-MII > ports, but use the (outer) tag on its MII port. I'm pretty sure I can do this on the 88e9095 by > re-configuring the DIX type (used to identify tagged frames on the non-MII ports) from 0x8100 to > something reserved. However, I won't know that this will work for sure till I get the eval board. You may also have to hack on the VLAN code a bit...I'm not sure it completely supports vlans in vlans, though it should be fairly straight-forward to add such support. Ben -- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com
