The value of vRtrIfGlobalIndex uniquely identifies this interface
in the tmnx system. This field provides an identifier for router
interfaces similar to the vRtrIfIndex value, except that vRtrIfIndex
is unique within each virtual router. The vRtrIfGlobalIndex is unique
system wide regardless of the vRtrID.
The vRtrIfGlobalIndex value for each virtual interface must remain
constant at least from one re-initialization of the system management
processor to the next.