vRtrIgmpIfSSMTransSrcAddr is an index into the table. It indicates
the source address for this group range. Whenever a (*,G) report is
received in the range specified by vRtrIgmpIfSSMTransGrpAddr1 and
vRtrIgmpIfSSMTransGrpAddr2, it is translated to an (S,G) report
with the value of this object as the source address.