Thanks Ben.   I ended up using a port in my Juniper to route traffic to
the other IP network/vlan which put the traffic back into the vlan at an
Untagged port.  Which is what one of the other responses hinted at, I
needed a layer 3 router in the mix.

Complicated setup, but at least I can control which ports receive the
multicast traffic and not hose my switch stacks.

Thanks,
 
Jake Gardner
TTC Network Administrator
Ext. 246

-----Original Message-----
From: Ben Scott [mailto:[EMAIL PROTECTED] 
Sent: Wednesday, November 19, 2008 2:24 PM
To: NT System Admin Issues
Subject: Re: vlan tagging

On Wed, Nov 19, 2008 at 10:42 AM, Jake Gardner <[EMAIL PROTECTED]>
wrote:
> All switches of VLan3 configured on the inbound and outbound ports.  
> Only the inbound port on the first 3812 is UNtagged, the rest are all
tagged.

  I'm not familiar with the 3Com switches, but it sounds like they work
just like our HP's do.  If so, the switch portsthe computers are plugged
into should be configured as UNtagged for the VLAN you want, *at both
ends*.  (Unless the computers are running a VLAN-aware network stack,
which I'm assuming they are not.)

  Explanation:

  Ethernet frames are either "tagged" or "untagged".  A tagged frame
means the frame has the VLAN tag prefixed to it, which identifies which
VLAN the frame is associated with.  An untagged frame is just a regular
Ethernet frame, with no VLAN information associated with it.

  If a port is configured as UNtagged for a VLAN, said port will emit
frames from said VLAN without a tag.  Said frames have nothing that
identifies them as coming from a VLAN.  This is useful for connecting
equipment which is *not* VLAN aware.  The equipment will just think it's
on a regular LAN, and talk to the switch as such.  The switch will
accept any untagged frames, and associate them with the UNtagged VLAN.

  If a port is configured as tagged for a VLAN, that means the port will
emit frames with the VLAN tag, and accept frames with VLAN tags, and
generally not do anything with VLANs for the computers.  The stuff
connected to said switch port needs to be VLAN aware.

  You can have multiple tagged VLANs for the same port, since the frames
have the tag that identifies which VLAN they are for.  You can only have
one untagged VLAN for a port, though.  The untagged VLAN means that
untagged frames correspond to that untagged VLAN.

  Hope this helps.

-- Ben

~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~
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