VTP - Code Field
Within the header of a VTP message, there is a field called "Code". This 8-bit code field is used to specify the type of VTP message being sent. The values used for these codes are version specific. For example, VTPv2 has the following codes, displayed in hexadecimal:
- 0x01 for summary advertisement
- 0x02 for subset advertisement
- 0x03 for an advertisement request
- 0x04: for a join message, used for pruning
VTP version 3 has additional codes that are sometimes unrecognized by packet sniffing software like Wireshark. For example, you may see something like this in a packet capture:
The value of 0x05 in the code field is unknown to Wireshark. This value is specific to VTPv3.
Links:
https://forum.networklessons.com/t/vtp-version-3/1225/62?u=lagapidis