08-28-2008 02:53 AM - edited 03-06-2019 01:02 AM
I have a question regarding the "show spanning-tree uplinkfast" command.
I know what uplinkfast does and how but I couldn't find documentation for the show-command.
A couple of switches in our network have an output like this one:
Command :show spanning-tree uplinkfast | i Number of
===============
Number of transitions via uplinkFast (all VLANs) : 51
Number of proxy multicast addresses transmitted (all VLANs) : 10920
If the transitions/multicasts are greater then 0, the backup-link must have been activated respectively the uplink must have been inactive, right?
This is what worries me, because I see many switches with counters > 0, and I normally wouldn't expect this in a stable network.
Solved! Go to Solution.
08-28-2008 12:51 PM
Hi Rolf,
An uplinkfast transition happens as a result of a configuration of the network (parameter change, link added/removed, switch reloaded etc...) or a failure (loss of bpdus, link going down etc...).
So if your sporadic uplinkfast transitions occur as a result of sporadic configuration events, I would not worry about them.
However, if you experience sporadic uplinkfast transitions while being sure that there is no configuration event, I would try to investigate their source.
Regards,
Francois
08-28-2008 09:10 AM
The most important is how those figures are evolving I guess.
If you have 51 vlans, it could be a single transition. If the alternate port(s) came up before the current root port, there might have been an uplinkfast transition without any failure. And this transition might have occurred 1 year ago;-) In that case you should not be worried.
On the other hand, you can have a single vlan that had its root port flapping 51 times in the last hour. In which case you might have indeed something going on.
It's impossible to make a difference between those two cases with just one snapshot.
Regards,
Francois
08-28-2008 11:25 AM
Francois,
thanks for the answer - this is an interesting point! We actually have nearly 50 VLANs and when I include all the default VLANs, it could be 51.
The reason why I'm monitoring things like that is that we sporadically see "Hostflapping" syslog messages and the MAC-Adress is always flapping between the uplink-port and a local access-port. First I couldn't understand how this can happen but now I'm convinced that it's related to this Uplinkfast swichovers.
And as long as this happens only sporadically I really don't have to worry, do I?
08-28-2008 12:51 PM
Hi Rolf,
An uplinkfast transition happens as a result of a configuration of the network (parameter change, link added/removed, switch reloaded etc...) or a failure (loss of bpdus, link going down etc...).
So if your sporadic uplinkfast transitions occur as a result of sporadic configuration events, I would not worry about them.
However, if you experience sporadic uplinkfast transitions while being sure that there is no configuration event, I would try to investigate their source.
Regards,
Francois
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