[c-nsp] VTP Pruning

[Bruce Pinsky]

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Dave Temkin wrote:
| Does anyone have a pointer to a doc that shows *how* VTP Pruning works?  I
| definitely know *what* it does, but none of the docs say how it determines
| whether or not a VLAN is in use...
|

I haven't found a public one that I can point you at.

| I had an issue years ago where even if there was an active port in a
| VLAN, it got pruned because the CAM entry fell out after awhile.  This
| broke things because it was in a one-way broadcast type environment
| (market data).  The general understanding is that if a port is active in
| that VLAN that it shouldn't be pruned....  But as I just stated, that
| wasn't the case in the past - and I'm not sure if that was a bug or if it
| was how it was intended to work....
|

According to the specs I've read, the pruning function is only notified of
the following events for local VLAN access ports:

- - Link state change of an access port
- - Port state change of an access port (i.e. admin status)
- - STP forwarding state change of a VLAN on access ports
- - VLAN membership change of an access port
- - Management VLAN changes

So having a valid CAM entry on a port in a VLAN does not appear to be one
of the criteria for considering that a VLAN is "active".

- --
=========
bep

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