Core issue
When the VLAN Trunking Protocol (VTP) mode is changed from VTP client mode to vtp transparent mode, the service providers loose Open Shortest Path First (OSPF) capabilities, but the IP connectivity is unaffected. The OSPF announcements becomes uni-directional.
The VTP transparent mode is needed when you want to configure an extended VLAN on the switch.
In many scenarios, this issue is due to VTP pruning enabled on the VTP server and thus, this impairs multicast hellos.
Resolution
Try this workaround in order to resolve this issue:
- Change the OSPF network type and hardcode neighbor statements into ospf config.
- Issue the no vtp pruning global configuration command in order to disable VTP pruning in the domain.
