I'm trying to extend the OOBM network through a VMM domain in order to access through the OOBM network to a virtual appliance hosted inside one esxi host.
I started "including" the VMM bridge domain to the Management tenant, i created the EPG... and i associated the port group that the apic created in the DVS with the virtual device management interface.
Then i tried to ping from the firewall to the OOBM Network GW and it fails.
I think that i miss something but i don't know what and i can not find any document explaining this...
How is your APIC oob connected into teh fabric? By default, oob is only going to take place on the dedicated interface on the apic. That is the only setting that is supported as of today.
With that in mind, the OOB plane is completely separate from the dataplane going through the Leaf node front panel ports. If you truly wanted to "tie oob in through the fabric", that would imply taking an oob switch and plugging that into the apic. That is something I would not advise given a production setup.
Assuming your goal is to get communication from the APIC to the Vcenter mgmt network through the fabric (data plane), you will want to work towards setting up inband mgmt. This is the type of configuration that will allow the apic to access mgmt of devices utilizing the leaf node data path.