Which two statements are true about IS-IS routing? (Choose two.)
A.
Based on the default timers, OSPF detects a failure faster than IS-IS does.
B.
OSPF default timers permit more tuning than IS-IS does.
C.
IS-IS is more efficient than OSPF in the use of CPU resources.
D.
OSPF is more scalable than IS-IS because of its ability to identify normal, stub, and
NSSA areas.
E.
IS-IS and OSPF are both Open Standard, link-state routing protocols which support
VLSM.
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 multi-access
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).