10-21-2009 02:48 AM - edited 03-06-2019 08:13 AM
Hi,
How does a downstream switch pass on the message to upstream switch that i dont have a particular VLAN , so dont pass any info about that VLAN.
regards
Neo
10-21-2009 02:57 AM
Neo,
The VTP Pruning is made by switches periodically (every 6 seconds or so) sending the VTP Join messages. Each of these messages contains a bit map in which the bit on i-th position signifies whether the VLAN number "i" is active on that switch. If a switch sends a VTP Join message to its neighbor having the i-th bit in the bit map set to 1, then that VLAN is active. If that bit is set to 0 then the VLAN is inactive and should be pruned. Simple, even naive, but working.
Best regards,
Peter
10-21-2009 08:28 AM
Hi Peter,
any URL where i can see the details for VTP Join message.your help will be apperciated
regards
Neo
10-21-2009 10:47 AM
Hello Neo,
You may want to read this URL for some information regarding the VTP:
http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml
However, regarding the VTP Join messages, there is no public information about it - at least I could not find any. The info I have posted earlier comes from my own small sniffing and reverse-engineering of the VTP traffic.
Best regards,
Peter
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