Hi Eddine ,
well in extreme we have inbound and and out of band vr.
vr-mgmt is used only for management purpose and uses management port only.
vr-default is used for in band traffic which is all front panel ports.
By default if you execute ping it goes through vr-Default ,
also to mention you can create your own Vr and add vlans/ports to it .
BR,
Aleixo