Re: [rbridge] announcing vlans question

On Mon, Feb 15, 2010 at 2:51 PM, Jeff Pickering <jeffpick@broadcom.com>wrote:

>  btw:  lets say an rb doesnt send any hellos per the case mentioned. Then
> lets say it enables a vlan on which
> nobody is avf. How does it send something to the DR to let it know that it
> shoudl get appointed?
>

It doesn't, at least not within the TRILL protocol as specified. But why is
it so important for a misconfigured RBridge to be able to try to get itself
made an appointed forwarder?

There is an Enabled VLANs sub-TLV that an RBridge can optionally include in
Hellos and that a DRB could use, if it was so implemented, as one element in
determining which RBridges to make appointed forwarders. Just fix the
configuration of this misconfigured RBridge and it could send that sub-TLV
in a Hello to the DRB. But how the DRB figures out or is configured to
appoint other RBridges on a link as appointed forwarders is left for
implementations to decide. By default, the DRB is the appointed forwarder
for all VLANs.

> Jeff
>

Thanks,
Donald

>  ------------------------------
> *From:* Donald Eastlake [mailto:d3e3e3@gmail.com]
> *Sent:* Monday, February 15, 2010 12:23 PM
> *To:* Jeff Pickering
> *Cc:* rbridge@postel.org
> *Subject:* 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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>