Indicating the mode in which the protected VLANs of an RRPP
domain are configured. The value 'vlan' indicates that
h3cRrppDomainProtectVlanListLow and h3cRrppDomainProtectVlanListHigh
can be used for setting protected VLANs, while
h3cRrppDomainInstanceListLow and h3cRrppDomainInstanceListHigh
cannot. By contraries, the value 'instance' indicates
that 3cRrppDomainInstanceListLow and h3cRrppDomainInstanceListHigh
can be used for setting protected VLANs while the other two cannot.