Re: [rbridge] announcing vlans question

Hi Jeff,

On Mon, Feb 15, 2010 at 9:18 AM, Jeff Pickering <jeffpick@broadcom.com>wrote:

>
> If a non-drb is configured to announce on all vlans, but does not have the
> vlan enabled that is the designated vlan
> announce by the drb, the non-drb will send helos only on vlan for which it
> is avf.
>

This is all on a per port basis.

I assume you mean by "configured to announce on all vlans" that the
Announcing Set for that port is set to all VLANs. Yes, in that case the
non-drb's port will send Hellos only on VLANs for which it is an appointed
forwarder.

Generally speaking, if there are RBridge ports that don't have the
designated VLAN enabled, arguably your network is mis-configured. Most
commonly one would expect all the RBridges in a campus to be configured to
designated the same VLAN if they are DRB and one would expect that that VLAN
would be enabled on all RBridge ports connected to inter-RBridge links. But,
of course, more complex configurations may be fine.

> But if such an rb is not avf on any
> vlans, it looks like it will send no hellos. Or does such an rb not accept
> the drb's desginated vlan in such a case?
> Is there text addressing this is the spec?  All I see is the following from
> 4.4.3:
>
>
> RBridges send TRILL Hellos Outer.VLAN tagged with
>    the Designated VLAN, unless that VLAN is not enabled on the port.
>

Right, the RBridge port does not send any Hellos, because sending Hellos
would generally just add useless traffic. Consider:

(1) Since the designated VLAN is disabled at the port, no inter-rbridge
traffic can flow through the port (i.e., no TRILL encapsulated data or LSPs
...)

(2) Since the port is not an appointed forwarder for any VLAN, no native
traffic can flow through the port (i.e., no data will be picked up and
encapsulated and no data will be decapsulated and sent.

So the port is basically orphaned from the link, although there still are
frames that could flow on the port, such as LLDP frames.

There was considerable controversy in the working group over how many Hellos
to send and the provisions in the current draft are the compromise that was
arrived at. The parenthetical at the top of page 51 of the draft
contemplates sending more Hellos than called for by the set operation
expressions.

Thanks,
Donald

Jeff
>
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