Subject: question about dot1qForwardAll/dot1qForwardUnregistered tables

From: steve shadix <[email-masked]>
Date: Thu, 22 Jul 1999 08:41:56 -0500

Hi,

I am in the process of implementing support for the 802.1Q MIB and
am having some confusion over the behavior associated with the
dot1qForwardAllTable and dot1qForwardUnregisteredTable. I am trying
to determine the actual effect these tables should have on the
forwarding
of multicast traffic. I have read and re-read the spec and the MIB but
at this point do not feel confident that I have a full (or even
half-full)
understanding of these objects. Any insight or information would be
greatly
appreciated.

My simplistic (probably overly simplistic) understanding of the
operation
is as follows (all objects are in same VLAN context):
    - If a packet is received for which a static address entry
      (dot1qStaticMulticastAddress) exist, it would be forwarded based
on
      the port list defined by dot1qStaticMulticastEgressPorts with no
      regard for set of ports defined by the dot1qForwardAllPorts or
      dot1qForwardUnregisteredPorts objects. What about ports that had
been
      added dynamically (i.e. ports that were not included in the
      dot1qMulticastForbiddenEgressPorts and had subsequently been added

      via GMRP) ?

    - If a packet is received for a dynamically registered multicast
address
      it would be forwarded to all ports the address had been registered
on as
      well as the set of ports included in the dot1qForwardAllPorts
object.

    - If a packet is received for an address for which there is not a
static
      entry or a dynamically registered entry it would be forwarded on
the set
      of ports included in the dot1qForwardUnregisteredPorts object and
      (this is where I'm really confused...) the set of ports included
in the
      dot1qForwardAllPorts object.

For example, assume a switch with 8 ports, all ports in forwarding state
and
all the information below is for a single VLAN:

    dot1qForwardAllPorts port list contains ports 2 and 3
    dot1qForwardUnregisteredPorts port list contains ports 4 and 5

    The filtering database contains:
    Static multicast address 1 (MC1) with ths following egress port
configuration:
        dot1qStaticMulticastEgressPorts : ports 6, 7
    Dynamically registered multicast address (MC2) : registered on ports
7, 8

Scenario 1:
  A packet is received on port 1 with a destination address of MC1.
Should
  it only be forwarded on ports 6 and 7 ?

Scenario 2:
  A packet is received on port 1 with a destination address of MC2.
Should
  it be forwarded on ports 2, 3, 7 and 8 ?

Scenario 3:
  A packet is recieved on port 1 with an destination address for which
there
  is no entry in the filtering database. Should this packet be forwarded
on
  ports 2, 3, 4 and 5 ?

Thanks for your assistance,
Steve Shadix
Wind River Systems
Dallas, TX