[rbridge] Preview of changes for VLANs, etc.

[Russ White]

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> - but without explicitly forbidding the use of a VLAN tag in 
> the link-level encapsulation required to get a frame from one
> RBridge to another.

Sure--If the only way to reach the next hop is through a vlan, then you
would need to encap in that vlan to get to the next hop. I think the
cleanest way to do this is:

1. Receive packet.
2. Look up exit rbridge.
3. Find next hop to the exit.
4. Look at the outbound interface towards this next hop.
5. If the outbound interface is a 1q interface (logical, rather than
physical), then encap with the inside vlan stuff, then the tunnel
header, then put it in another tunnel header, with the destination
address being the next hop, and the vlan stuff being the correct one to
reach that next hop.
6. If the outbound interface is not a 1q interface (physical, rather
than logical), then encap with the vlan stuff, then the tunnel header
for the outer edge rbridge (egress rbridge), and forward it.

When the next hop receives the packet in the case of #5, it will see the
packet is to it, strip the outer header, and then see the inner tunnel,
and forward the packet according to local rules, based on it's tree,
etc. I think this is much simpler than having a "set" vlan on any given
link, or having to carry around a set of vlans you forward for, and such.

:-)

Russ

- --
riw at cisco.com CCIE <>< Grace Alone

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