04-05-2013 06:56 PM - edited 03-07-2019 12:40 PM
Hi everybody.
Let suppose our switch receives an inferior bpdu on its current root port. Our sw starts sending RLQ out of its all blocked ports.
My question is how long a switch waits for a RLQ reply on these blocked ports ? ( obviously sw can not wait forever for these RLQ replies, there ought to be some timeout value).
As usual have a great weekend.
Solved! Go to Solution.
04-06-2013 07:10 AM
Hi Sarah,
From the spanning tree document:
When an inferior BPDU is detected on a non-designated port, the second phase of backbone fast is triggered. Instead of passively waiting max_age to age out ports that can be affected by the failure, a proactive way to test them immediately is introduced by means of the RLQ PDU. The RLQ is used to achieve a kind of ping for the root on a non-designated port and allowed to quickly confirm if the BPDU stored on a port is still valid or needs to be discarded.
So, I would say the switch replies to the RLQ immediately.
here is the doc:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800c2548.shtml
HTH
Have a nice weekend
04-06-2013 12:36 AM
Hi,
I think the process has to stop at the latest when MAX_AGE expires.
If you search for patent US 6219739, you can find a lot of information about the mechanisms.
Best regards
Rolf
04-06-2013 07:10 AM
Hi Sarah,
From the spanning tree document:
When an inferior BPDU is detected on a non-designated port, the second phase of backbone fast is triggered. Instead of passively waiting max_age to age out ports that can be affected by the failure, a proactive way to test them immediately is introduced by means of the RLQ PDU. The RLQ is used to achieve a kind of ping for the root on a non-designated port and allowed to quickly confirm if the BPDU stored on a port is still valid or needs to be discarded.
So, I would say the switch replies to the RLQ immediately.
here is the doc:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800c2548.shtml
HTH
Have a nice weekend
04-06-2013 10:54 PM
Hi Reza
what if the rlq reply is lost or filtered.then how long a switch waits for rlq reply before giving up?
have a great weekend.
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