Have a strange situation I never came across. Customer has a bunch of switches and is not paying attention when he sets them up so they are all in VTP server mode (default) with no domain specified.
He plugs in another switch with a VTP domain specified. He then reports that all the switches are now in this VTP domain. I would have thought that with no domain specified they would have to specifically be told that they are servers in a VTP domain.
Working as expected:
By default, the switch is in the VTP no-management-domain state until it receives an advertisement for a domain over a trunk link (a link that carries the traffic of multiple VLANs) or until you configure a domain name. Until the management domain name is specified or learned, you cannot create or modify VLANs on a VTP server, and VLAN information is not propagated over the network.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and the VTP configuration revision number. The switch then ignores advertisements with a different domain name or an earlier configuration revision number.
Nope that is normal if the vtp domain name is at the factory null domain. The first vtp advertisement it recieves it will take that vtp name and input it into the vlan.dat file. Did it assume all the the vlans too ?