The value of vRtrType specifies the type of virtual router
represented by this row entry. When a row is created in this
table using 'createAndGo', vRtrType must be specified or the
row creation will fail.
Only the value of 'vr (3)' can be set with a SNMP SET request.
The other values are used for row entries created internally by
the agent.
The value of vRtrType cannot be modified if vRtrRowStatus has
a value of 'active'.