hm2RingRedSecondaryIntf

This textual convention is an extension of the
InterfaceIndex convention.  The latter defines a greater
than zero value used to identify an interface or interface
sub-layer in the managed system.  This extension permits the
additional value of zero.  the value zero is object-specific
and must therefore be defined as part of the description of
any object which uses this syntax.  Examples of the usage of
zero might include situations where interface was unknown,
or when none or all interfaces need to be referenced.