Data Traffic Blocked between VTP Domains Sometimes it is required to connect to switches that belong to two different VTP domains. For example, there are two switches called Switch1 and Switch2. Switch1 belongs to VTP domain cisco1 and Switch2 belongs to VTP domain cisco2. When you configure trunk between these two switches with the Dynamic Trunk Negotiation (DTP), the trunk negotiation fails and the trunk between the switches does not form, because the DTP sends the VTP domain name in a DTP packet. Because of this, the data traffic does not pass between the switches. https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98155-tshoot-vlan.html#topic5