Cisco CID Exam Certification Guide

Mike Crane, CCIETM and Reggie Terrell

Appendix A

Answers to "Do I Know This Already" Quiz

Chapter 1

  1. What are the goals of an internetwork design?

Functionality.

Scalability.

Adaptability.

Manageability.

Cost-effectiveness.

  1. What trade-off is present in every network design?

Cost versus availability.

  1. What are the three layers of the hierarchical model?

Core.

Distribution.

Access.

  1. Where should redundancy be prioritized?

The primary focus of redundancy should be on the WAN link. Configure the WAN as a top priority for maximum availability.

  1. What layer acts as the intermediate layer in the hierarchical model?

The distribution layer is the intermediate layer between the core layer and the access layer. The distribution layer is the recommended place for access lists and security functions.

  1. True or false: After implementing the network, the CCDP should consider the task complete.

False. After the implementation phase, the network must be monitored. During the monitoring phase, the customer should concur that the network is functioning according to design specifications.

  1. What Cisco router is recommended for the Core layer?

Cisco 7000 and above.

  1. What is the simplest internetwork design model?

Flat-earth design.

  1. What is the most significant cost component of an internetwork over time?

Internetwork support is the most significant cost component for an internetwork over time.

  1. Why is protocol selection important with regard to network design?

Protocols can consume large quantities of bandwidth due to broadcasts. If a station spends too much time processing broadcasts, the network can become efficient.

  1. What are the recommended steps for designing an internetwork?

Gather information.

Analyze requirements.

Develop the internetwork structure.

Estimate network performance.

Assess costs and risks.

Implement and monitor the network.

  1. What benefits can be gained by using the hierarchical model?

Scalability.

Ease of troubleshooting.

Protocol support.

Manageability.

  1. Name a Cisco router that can be employed at each layer of the hierarchical model.

Core – Cisco 7000 and 12000 series routers.

Distribution – Cisco 4000 series routers.

Access – Cisco 1000 and 2500 series routers.

  1. What layer of the network is primarily concerned with high-speed transport of data?

Core layer.

Chapter 2

  1. What is the first step in campus network design?

Identifying the business and technical requirements.

  1. What two backbones are the recommended models for the Campus LAN design?

Distributed and collapsed.

  1. What business issues govern the design acceptance process?

Business issues are governed by cost. In addition to fixed equipment costs, recurring costs must be considered. Determining the total cost of ownership is critical to ensuring the long-term success of the network.

  1. What three categories of problems do most networks fall into?

Most problems can be attributed to media, protocols, or transport.

  1. What are the two largest factors in determining network design?

Cost and availability.

  1. Why are desktop protocols least desirable for a large network?

Desktop protocols tie up large quantities of bandwidth with broadcasts. Excessive broadcasts can render the network inefficient.

  1. What solution should the CCDP employ when addressing a network with media contention?

Switches.

  1. When might an ATM switch improve an internetwork’s design and performance?

For networks that require Quality of Service delivery.

  1. What device should be used to filter broadcasts and multicasts?

Router.

  1. What is the difference between a broadcast domain and a bandwidth domain?

A bandwidth domain consists of all traffic associated with a single port on a bridge or switch. A broadcast domain consists of all traffic associated with a single port on a router.

  1. What issues should you address when designing a campus LAN?

Server and client end stations.

Network infrastructure.

Network management.

Business concerns.

  1. How can a VLAN improve network performance?

A VLAN isolates bandwidth segments. So, one user or a group of users who require large amounts of bandwidth will not impact network performance for the rest of the network.

  1. What device controls broadcasts and multicasts?

Router.

  1. Name two protocols that are not recommended for WAN design.

NetBEUI and AppleTalk.

  1. What protocol is recommended for use on the Internet?

TCP/IP.

Chapter 3

  1. Name four campus LAN technologies.

Ethernet, Token Ring, FDDI, ATM.

  1. State a major disadvantage of using Ethernet.

Ethernet allows collisions to occur on the network. An excessive number of collisions reduces available bandwidth.

  1. List two LAN interconnection methods.

Bridging, switching and routing.

  1. What are two types of switching methods for Ethernet?

Cut-through and store and forward.

  1. State four goals that you can achieve by using switches in a campus LAN.

Reducing network congestion while increasing the available bandwidth.

Organizing users into logical workgroups.

Reducing the costs of managing network operations.

Providing scalability, traffic control, and security.

  1. Bridges operate at Layer ___ of the OSI model and forward ______.

2, frames.

  1. Name three primary types of cable used in LANs.

Coaxial, twisted-pair, fiber-optic.

  1. Routers operate at Layer ___ of the OSI model and forward ______.

3, packets.

  1. List three types of wireless networks.

Infrared, laser, point-to-point transmission.

  1. How are traffic loops prevented on switches and routers?

STP, split horizon, poison reverse.

  1. What cable is recommended for wiring between closet and campus buildings?

Fiber-optic.

  1. What cable is recommended for transmitting data at very high speeds over long distances?

Fiber-Optic.

  1. What is the Cisco proprietary protocol for connecting Cisco switches?

ISL.

  1. List three functions provided by routers.

Segmenting LANs and WANs.

Determining the best path to the destination.

Communicating route information with other routers.

  1. What are some benefits of designing a network with Thinnet?

Relatively inexpensive.

Easy to install.

Easy to configure.

Chapter 4

  1. What is the size of an ATM cell, and how do its fixed length and size contribute to low latency?

The ATM cell has a fixed length of 53 bytes—48 for the data and 5 for the header. With the fixed length, the ATM switch doesn’t have to be notified when the transmission is done. So, the ATM switch doesn’t waste overhead looking for information in software.

  1. What are the two types of virtual circuits used by ATM?

ATM’s flexibility allows it to run on permanent virtual circuits and switched virtual circuits.

  1. Name and describe the three layers of the ATM reference model.

The three layers of the ATM reference model are the ATM physical layer, the ATM layer, and the ATM adaptation layer (AAL). These three layers correlate to the physical and data link layers of the OSI model. The AAL is responsible for allowing data conversions from multiple applications to and from the ATM cell.

  1. What layer of the OSI model closely relates to the ATM reference model?

The ATM physical layer closely relates to the physical layer (Layer 1) in the OSI model.

  1. For each application listed, match the ATM Adaptation Layer best suited to it:

VoiceAAL 1
SMDSAAL 2
DataAAL 3/4
AAL 5

Voice = AAL 1
SMDS = AAL 3/4
Data = AAL 5

  1. Name the four major components of ATM LANE.

LECS (LAN Emulation Configuration Server).

LEC (LAN Emulation Client).

LES (LAN Emulation Server).

BUS (Broadcast and Unknown Server).

  1. For what two LAN clients does ATM LANE provide emulation?

Ethernet and Token Ring.

  1. What two types of interfaces are described in the ATM model?

User Network Interface (UNI).

Network-to-Network Interface (NNI).

  1. Name four alternative models for ATM internetworking.

Local Area Network Emulation (LANE).

A point-to-point data link.

A high-speed workgroup and backbone.

A router cluster backbone.

  1. Name four networking areas where ATM could be implemented.

Campus, local area, wide area, metropolitan.

  1. What protocol controls the user cell stream between nodes and networks?

Private Network-Node Interface (intranetwork) or Private Network-Network Interface (internetwork)(PNNI).

  1. How many characters comprise an NSAP address?

20 octet or 40 hex.

  1. What is Interim Local Management Interface (ILMI), and how is it used to connect end stations?

ILMI allows two systems to exchange ATM information. LECs use ILMI to locate the LECs and to determine their own address.

  1. Name four Cisco products that can form the building blocks of an ATM WAN.

Cisco/StrataCom IGX switch, which is well-suited for deployment in an enterprise WAN environment.

Cisco/StrataCom BPX/AXIS switch, which meets the needs of high-end enterprise WAN and service provider environments.

Cisco AIP for the Cisco 7500 and 7000 series of routers.

Cisco ATM Network Interface Module (NIM) for the Cisco 4700 and 4500 series of routers.

  1. Name two business and technical requirements that might lead an engineer to select ATM as a design solution.

Business requirement: Distance learning and training.

Business requirement: Video on demand.

Technical requirement: Single multiservice enterprise solution granting voice, data, and video with Quality of Service.

Technical requirement: Greater bandwidth on demand to satisfy bandwidth-intensive applications.

Chapter 5

  1. What are the five IP address classes?

Classes A, B, C, D, and E.

  1. What class of IP address is optimum for a small network?

Class C.

  1. Which IP addresses are reserved for multicasting?

224.0.0.0 to 239.255.255.255.

  1. What IP address class renders 254 hosts?

Class C.

  1. Which IP addresses are reserved for experiments?

240.0.0.0 to 254.255.255.255.

  1. What is NAT, and how can it help conserve IP addresses?

Network Address Translation (NAT) allows unregistered addresses in a private domain to be translated to a registered public address.

  1. List four benefits of address summarization.

Reduces the size of the routing table.

Hiding network changes.

Network growth.

Reduces router resource utilization.

  1. What subnet mask is ideal for connecting WAN links?

255.255.255.252 (/30) mask. It provides two hosts. On the WAN, serial lines require only two host addresses.

  1. Define classful routing.

Classful routing observes the class address boundaries of Classes A, B, and C. Classful routing protocols cannot carry variable-subnet mask information in their updates.

  1. What is CIDR, and how does it offer greater flexibility in IP addressing?

Classless interdomain routing (CIDR) allows for the reduction of the size of routing tables by creating aggregate routes, or supernets. CIDR eliminates the concept of network classes and allows for better scalability when supporting the advertising of IP prefixes in the Internet.

  1. What is a discontiguous subnet?

A discontiguous subnet is two or more portions of a major network that are separated by another major network.

  1. True or false: To support variable-length subnet masking and route summarization, a classless routing protocol must be incorporated into the design plan.

True.

  1. Define classless routing.

Classless routing allows the prefix to be increased from the fixed classful length. Classless routing allows prefixes to be greater than the classful specifications of 8, 16, and 24.

  1. What is the prefix length of a Class A network?

8 bits.

  1. The network design requires 14 hosts. What network and subnet mask should be employed?

255.255.255.240.

Chapter 6

  1. List five possible requirements for a routing protocol.

Should adapt to change easily and quickly.

Does not create a lot of traffic.

Scales to a large size.

Based on industry standards.

Compatible with existing hosts and routers.

  1. What two tasks do routers perform?

Switching frames and path determination.

  1. What is the simplest form of routing?

Static routing.

  1. What type of routing determines the best path?

Dynamic routing.

  1. List four types of interior gateway protocols.

RIP, OSPF, IGRP, EIGRP.

  1. What is administrative distance?

Administrative distance can be defined as a rating of the trustworthiness of a routing information source. Numerically, an administrative distance is an integer between 0 and 255. The higher the value, the lower the trust rating.

  1. What protocol works primarily in the Internet?

BGP.

  1. List three types of routing metrics.

Hop count, delay, bandwidth.

  1. What is a classless protocol?

Classless protocols support VLSMs and include network masks in their routing updates. Classless protocols are not restricted by class boundaries.

  1. List one disadvantage of classful routing protocols.

The whole network must use the same network class mask.

  1. List three types of switching methods used by Cisco routers.

Process switching, fast switching, autonomous switching.

  1. What is the routing metric for OSPF?

Cost.

  1. List three requirements of route summarization.

Multiple IP addresses must share the same high-order bits.

Routing protcols must carry the prefix length or subnet mask in a separate field along with the 32-bit IP address.

Routing tables and protocols must base their routing decisions on a 32-bit IP address with a prefix length that can be up to the entire 32-bit length of the field.

  1. True or false: Secondary addressing is a recommended and preferred method of connecting discontiguous subnets.

False. Secondary addressing consumes resources. Use secondary addressing as a last resort and as a temporary resort.

  1. ______is the exchange of routing information between two different routing processes.

Route redistribution.

Chapter 7

  1. What limitations of RIP, the first Internet routing protocol, was OSPF designed to overcome?

Limited range of 15 hops.

Slow convergence.

Susceptibility to routing loops.

  1. What are the four types of connections for the OSPF routing protocol?

Point-to-point.

Point-to-multipoint.

Broadcast.

Nonbroadcast.

  1. Name the four classifications of OSPF routers.

Internal.

Area border router (ABR).

Area system border router (ASBR).

Backbone router.

  1. What are link-state advertisements? Name four types of link-state advertisements.

Link State Advertisements (LSAs) advertise the state of the link to other OSPF routers.

Router LSA—Type 1 LSAs contain information about router links, interfaces, state of links, and cost.

Network LSA—Type 2 LSAs contain lists of routers connected to a multiaccess network segment.

Summary LSA—Type 3 LSAs originate at area border routers and are sent into an area to advertise networks that have been summarized into a single route.

Summary LSA (ASBR)—Type 4 LSAs originate as area system border routers and are sent to networks that have been summarized into a single route to the OSPF network to advertise the ASBR.

AS-external LSA—Type 5 LSAs contain information that describes destinations external to the OSPF AS.

  1. True or false: All OSPF areas must be physically adjacent to the backbone.

False. Virtual links can connect areas that are not physically attached to the backbone.

  1. The following are OSPF routes. Perform summarization to one route. What configuration commands would be needed if the routes were external? What commands would be needed if the routes were internal?
  • Route 1172.26.30.0
  • Route 2172.26.31.0
  • Route 3172.26.32.0

External routes: summary address 172.26.0.0 255.255.192.0

Internal routes: area 1 range 172.26.0.0 255.255.192.0

  1. Compare and contrast stub, totally stubby, and not-so-stubby areas.

In a stub area, a default route summarizes all external routes. Stub areas are similar to regular areas, except that the routers do not enter external routes in the area’s databases. Type 3 LSAs are still flooded into the area.

A totally stubby area only allows the default summary link to be propagated into the area by the ARB. Type 3 LSAs are not flooded into the area.

Not-so-stubby areas are similar to stub areas, except that they allow limited importing of external routes.

  1. List six rules for designing a scalable OSPF internetwork.

No more than six hops from source to destination.

50 routers per area.

All areas connect to Area 0.

Do not allow more than two areas per ABR.

Use totally stubby areas.

Maximize summarization.

  1. How does OSPF route summarization save router resources?

Summarization reduces the memory and the CPU processing load on the routers.

  1. What is the meaning of cost, and how does OSPF calculate cost?

Cost is the metric that OSPF uses to determine the shortest path. The metric is added from source to destination over all outgoing links. OSPF defines cost as 10 E8/BW.

  1. What is the difference between an External Type 1 route and an External Type 2 route?

External Type 1 routes use a metric that is the sum of the external metric and the collective internal cost of reaching the destination.

External Type 2 routes use a metric that examines the external metric and does not take the internal cost into consideration.

  1. Which routing protocols are supported by EIGRP?

IP, IPX, AppleTalk.

  1. EIGRP updates are

A. periodic

B. incremental

C. A and B

D. None of the above

Answer is B, incremental

  1. Name five values that IGRP and EIGRP use to determine metrics. Which metrics are used by default?

By default, IGRP metric = bandwidth + delay.

In addition to bandwidth and delay, IGRP can be configured to track the following metrics:

Reliability.

Loading.

MTU (static).

  1. Name two parameters that can be tuned by IGRP to allow faster convergence.

Turning off or reducing holddown.

Reducing the update timer.

Chapter 8

  1. In what situations is AppleTalk recommended?

AppleTalk is recommended when the goal is to design a small network to support Apple computers that is easy to use, configure, and maintain.

  1. Name two AppleTalk protocols that operate at the network layer.

AppleTalk Address Resolution Protocol (AARP).

Datagram Delivery Protocol (DDP).

  1. What three elements comprise an AppleTalk network address?

Network number, node number, socket number.