748 Appendix A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
15
Identify reasons for using tunneling.
The four reasons outlined in this text are these:
·
To allow multiprotocol traffic to flow over an IP backbone
·
To support VPNs
·
To overcome discontiguous network problems
·
To overcome the shortcoming of some routing protocols with low maximum metric
limitations
Other reasons may also be valid because this question is somewhat subjective.
16
What tunneling transport protocol is used by the IOS?
To answer this question, you must understand the term transport protocol. Transport
protocol refers to the protocol that encapsulates the data and transports the data to the
other side of the tunnel. There is only one transport protocol in the IOS: IP.
Answers to the Chapter 6 Q&A Section
1
What type of routing protocol algorithm uses a holddown timer? What is its purpose?
Distance vector. Holddown helps prevent counting to infinity problems. Holddown is
explained in detail in the section "Distance Vector Routing Protocols" in Chapter 6. After
hearing that a route has failed, a router waits for holddown time before believing any new
information about the route.
2
Define what split horizon means to the contents of a routing update. Does this apply to
both the distance vector algorithm and the link state algorithm?
Routing updates sent out an interface do not contain routing information about subnets
learned from updates entering the same interface. Split horizon is used only by distance
vector routing protocols.
3
Write down the steps you would take to migrate from RIP to IGRP in a router whose
current RIP configuration includes only router rip, followed by a network 10.0.0.0
command.
Issue the following commands in configuration mode:
router igrp 5
network 10.0.0.0
no router rip
apA.fm Page 748 Monday, March 20, 2000 5:24 PM