Authentication on 1500d through Mgt1 didn't work.

Hello,

I'm working on installation of clustering of Fortigate 1500D and I have some questions.

My clustering will route a network management out of band where all my network devices will be connected.

For this point I have a VDOM with this VLAN attached to interfaces (no problem at this point).

My both Fortinet have their interface Mgt1 with IP on this subnet and attached  to a switch connected to this VLAN.

My problem is the following:

 I would like to activate Tacacs+ on Mgt1 (because i want to manage my 1500D by this port). But it didn't work.

Can someone can help me to understand why it didn't work and how I can resolve my problem?

Thank you for your help.

Best Regard,

Matthieu