VTP Advertisements

VTP advertisements can occur in three forms:

1. Summary advertisement
1. every 5 minutes
2. information included
1. VTP version
2. domain name
3. configuration revision number
4. time stamp
5. MD5 encryption  hash code
6. number of subset advertisements to follow
3. Subset advertisement
1. sent after VLAN configuration changed.
2. information included:
1. VTP version
2. Subset sequence number 
3. domain name
4. configuration revision number
5. VLAN info field
2. Advertisement requests from clients
1. VTP client can request the VLAN information it lacks.

CCNP SWITCH 642-813 I\Official Certification Guide

Difference between VTP versions

VTP version 1:

• Supports normal VLAN numbers (1-1001)
• Supports pruning of unused VLANs (no longer sends broadcasts and unknown unicasts
• supports cleartext and MD5 digest password

VTP version 2:

• Forwards the VTP messages without checking the version number or domain in transparent mode
• Supports Token Ring
• Performs consistency check on the VTP / VLAN parameters (from CLI or SNMP)
• Pass on Unrecognised TLVs

VTP version 3:

• Supports extended VLAN numbers (1-4095)
• Transfer information regarding Private VLAN structure
• Support for databases other than VLAN (for example MST)
• Protection from unintended database overrides during insertion of new switches
• Hidden password protection

- CCNP SWITCH 642-813 Official Certification Guide

- http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/solution_guide_c78_508010.html