Final answer:
RIPv1 does not support VLSM, while RIPv2, IGRP, EIGRP, OSPF, and IS-IS all support it, with RIPv2, EIGRP, OSPF, and IS-IS being the protocols that more effectively utilize VLSM.
Step-by-step explanation:
The routing protocol that does NOT support VLSM (variable length subnet masking) among the choices given is RIPv1. RIPv1 is an older routing protocol that does not support VLSM as it is classful and sends updates without subnet mask information. On the other hand, RIPv2, IGRP, EIGRP, OSPF, and IS-IS all support VLSM. RIPv2 was an enhancement over RIPv1 that added support for VLSM, among other features. IGRP, although older, did have some basic VLSM support which was then enhanced in its successor EIGRP. Both OSPF and IS-IS are link-state protocols that inherently support VLSM.