Which two are characteristics of the IS-IS protocol but not OSPF? (Choose two.)
A.
forms adjacencies with all neighbors
B.
supports demand circuit routing
C.
provides routing support for multiple network layer protocols
D.
utilizes SPF algorithm
E.
provides for network scalability by allowing the network to be separated into areas
F.
three layers of hierarchical routing
Explanation:
IS-IS is the dynamic link-state routing protocol for the OSI protocol stack. As such, IS-IS
distributes routing information for routing CLNP data for the ISO CLNS environment. When
IS-IS is used strictly for the ISO CLNS environment, it is referred to as ISO IS-IS.
Differences between IS-IS and OSPF.
Although IS-IS and OSPF share many common features, they do have quite a few
differences:
• Whereas OSPF routers can be part of multiple areas, an IS-IS router belongs to only
one area per routing process.
• In OSPF, the boundaries of areas are set in the router. The boundaries of areas are
on the network connections between routers for IS-IS, reiterating that each router is in only
one area per routing process.
• IS-IS utilizes CLNS protocol data units (PDUs) to send information between routers
instead of using IP packets, like OSPF does.
• IS-IS allows for the preempting of DRs, where OSPF does not.
• OSPF DROthers do not form adjacencies with other DROthers on broadcast multiaccess networks, while in the same environment, all IS-IS intermediate systems form
adjacencies with one another.
The backbone of an IS-IS network is designated by the type of routers in it instead of being
designated by an area number (0, in the case of OSPF).