CCDA

QoS Mechanisms for VoIP Networks

Cisco provides different QoS tools that you should use on edge and backbone routers to support VoIP networks. This section covers several QoS mechanisms and their impact on VoIP networks Priority Queue-WFQ (PQ-WFQ) CRTP was covered in an earlier section. It compresses the IP UDP RTP headers from 40 bytes to 2 or 4 bytes. It is configured on a link-to-link basis. Cisco recommends using CRTP for links lower than 768 kbps. Do not configure CRTP if the router CPU is above 75 percent utilization....

Best Practices for Hierarchical Layers

Each layer of the hierarchical architecture contains special considerations. The following sections describe best practices for each of the three layers of the hierarchical architecture access, distribution, and core. When designing the building access layer, you must take into consideration the number of users or ports required to size up the LAN switch. Connectivity speed for each host should be considered. Hosts might be connected using various technologies such as Fast Ethernet, Gigabit...

CAS and CCS Signaling

Digital signaling has two major forms Channel Associated Signaling (CAS) and Common Channel Signaling (CCS). The major difference is that with CAS the signaling is included in the same channel as the voice call. With CCS the signaling is provided in a separate channel. Table 15-2 shows the common types of CAS and CCS. They are covered in the following sections. Table 15-2 Common CAS and CCS Signaling Types Table 15-2 Common CAS and CCS Signaling Types

Hierarchical Network Design

As shown in Figure 2-1, a traditional hierarchical LAN design has three layers The core layer provides fast transport between distribution switches within the enterprise campus. The distribution layer provides policy-based connectivity. The access layer provides workgroup and user access to the network. Figure 2-1 Hierarchical Network Design Has Three Layers Core, Distribution, and Access Each layer provides necessary functionality to the enterprise campus network. You do not need to implement...

WLAN Controller Components

The CCDA candidate must understand the three major components of WLCs Wireless LANs are identified by unique SSID network names. The LAN is a logical entity. Each WLAN is assigned to an interface in the WLC. Each WLAN is configured with radio policies, QoS, and other WLAN parameters. A WLC interface is a logical connection that maps to a VLAN on the wired network. Each interface is configured with a unique IP address, default gateways, physical ports, VLAN tag, and DHCP server. The port is a...

Roaming and Mobility Groups

The primary reason to have wireless networks is the ability to access network resources from common areas and in areas difficult to run cables. End clients might want to move from one location to another. Mobility allows users to access the network from several locations. Roaming occurs when the wireless client changes association from one access point to another. The challenge is to scale the wireless network to allow client roaming. Roaming can be intracontroller or intercontroller....

Radio Management and Radio Groups

The limit of available channels in the ISM frequencies used by the IEEE 802.11b g standard presents challenges to the network designer. There are three nonoverlapping channels (channels 1, 6, and 11). The recommended best practice per AP is up to 20 data devices, or no more than seven concurrent voice over WLAN (VoWLAN) calls using g.711 or eight concurrent VoWLAN calls using g.729. Additional APs should be added as user population grows to maintain this ratio of data and voice per AP. Cisco...

Do I Know This Already Uxu

You use External Border Gateway Protocol (eBGP) to exchange routes between autonomous systems. 2. C. The current version of BGP is Version 4. BGPv4 includes support for CIDR. 3. B. It is a best practice to summarize routes on the distribution routers toward the core. 4. D. PBR changes packets' routes based on configured policies. 5. B. You use IGMP between hosts and local routers to register with multicast groups. B. The lower 23 bits of the IP multicast address are mapped to the last 23...

References and Recommended Readings Rey

RFC 1349, Type of Service in the Internet Protocol Suite. Available from http www.ietf.org rfc. Croft, B. and J. Gilmore. RFC 951, Bootstrap Protocol (BOOTP). Available from http www.ietf.org rfc. Davie, B., A. Charny, J.C.R. Bennet, K. Benson, J.Y. Le Boudec, W. Courtney, S. Davari, V. Firoiu, and D. Stiliadis. RFC 3246, An Expedited Forwarding PHB (Per-Hop Behavior). Available from http www.ietf.org rfc. Droms, R. RFC 2131, Dynamic Host Configuration Protocol. Available from http...

Digital Subscriber Line

Digital Subscriber Line (DSL) is a technology that provides high-speed Internet data services over ordinary copper telephone lines. It achieves this by using frequencies that are not used in normal voice telephone calls. The term xDSL describes the various competing forms of DSL available today. Some of the DSL technologies available include asymmetric (ADSL), symmetric (SDSL), high bit rate (HDSL), very high bit rate (VDSL), rate-adaptive (RADSL) and IDSL (based on ISDN). Table 5-3 summarizes...

Pv4 Address Classes

IPv4 addresses have five classes A, B, C, D, and E. In classful addressing, the most significant bits of the first byte determine the address class of the IP address. Table 7-8 shows the high-order bits of each IP address class. Table 7-8 High-Order Bits of IPv4 Address Classes Table 7-8 High-Order Bits of IPv4 Address Classes *x can be either 1 or 0, regardless of the address class. *x can be either 1 or 0, regardless of the address class. Again, the IPv4 Class A, B, and C addresses are...

Ethernet Design Rules

Ethernet is the underlying basis for the technologies most widely used in LANs. In the 1980s and early 1990s, most networks used 10-Mbps Ethernet, defined initially by Digital, Intel, and Xerox (DIX Ethernet Version II) and later by the IEEE 802.3 working group. The IEEE 802.3-2002 standard contains physical specifications for Ethernet technologies through 10 Gbps. Table 3-2 describes the physical Ethernet specifications up to 100 Mbps. It provides scalability information that you can use when...

Pv4 Header

The best way to understand IPv4 is to know the IPv4 header and all its fields. Segments from TCP or the User Datagram Protocol (UDP) are passed on to IP for processing. The IP header is appended to the TCP or UDP segment. The TCP or UDP segment then becomes the IP data. The IPv4 header is 20 bytes in length when it uses no optional fields. The IP header includes the addresses of the sending host and destination host. It also includes the upper-layer protocol, a field for prioritization, and a...

RIPv2 Message Format

The RIPv2 message format takes advantage of the unused fields in the RIPvl message format by adding subnet masks and other information. Figure 10-3 shows the RIPv2 message format. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 IP address (2nd route entry - up to 25) Command Indicates whether the packet is a request or response message. The request message asks that a router send all or a part of its routing table. Response messages contain route entries. The router sends the...

Administrative Distance

On Cisco routers running more than one routing protocol, it is possible for two different routing protocols to have a route to the same destination. Cisco routers assign each routing protocol an administrative distance. When multiple routes exist for a destination, the router selects the longest match. For example, if to reach a destination of 170.20.10.1 OSPF has a route prefix of 170.20.10.0 24 and EIGRP has a route prefix of 170.20.0.0 16, the OSPF route is preferred because the 24 prefix is...

ISIS Operation and Design

This subsection discusses IS-IS areas, designated routers, authentication, and the NET. IS-IS defines areas differently from OSPF area boundaries are links and not routers. IS-IS has no BDRs. Because IS-IS is an OSI protocol, it uses a NET to identify each router. To configure the IS-IS routing protocol, you must configure a NET on every router. Although configuring NET is not a CCDA test requirement, this information is included for extra credit. Although you can configure IS-IS to route IP,...

LAN Design Types and Models

LANs can be classified as large-building LANs, campus LANs, or small and remote LANs. The large-building LAN typically contains a major data center with high-speed access and floor communications closets the large-building LAN is usually the headquarters in larger companies. Campus LANs provide connectivity between buildings on a campus. Redundancy is usually a requirement in large-building and campus LAN deployments. Small and remote LANs provide connectivity to remote offices with a...

Large Building LANs

Large-building LANs are segmented by floors or departments. The building-access component serves one or more departments or floors. The building-distribution component serves one or more building-access components. Campus and building backbone devices connect the data center, building-distribution components, and the Enterprise Edge-distribution component. The access layer typically uses Layer 2 switches to contain costs, with more expensive Layer 3 switches in the distribution layer to provide...

Pv6 Multicast Addresses

IPv6 retains the use and function of multicast addresses as a major address class. IPv6 prefix FF00 8 is allocated for all IPv6 multicast addresses. IPv6 multicast addresses are described in RFC 2373. EIGRP for IPv6, OSPFv3, and RIPng routing protocols use multicast addresses to communicate between router neighbors. The format of the IPv6 multicast address is described in Chapter 8, Internet Protocol Version 6. The common multicast addresses are repeated in Table 12-3. Table 12-3 Well-Known...

Cisco Enterprise Architecture Model

The Cisco Enterprise Architecture model facilitates the design of larger, more scalable networks. It represents the focused views of the Cisco Service-Oriented Network Architecture (SONA), which concentrates on each area of the network. SONA is covered in Chapter 1, Network Design Methodology. As networks become more sophisticated, it is necessary to use a more modular approach to design than just WAN and LAN core, distribution, and access layers. The architecture divides the network into...

Service Provider SP Edge Module

The SP Edge module, shown in Figure 2-11, consists of SP edge services such as the following Enterprises use SPs to acquire network services. ISPs offer enterprises access to the Internet. ISPs can route the enterprise's networks to their network and to upstream and peer Internet providers. Some ISPs can provide Internet services with DSL access. Connectivity with multiple ISPs was described in the Internet Edge section. For voice services, PSTN providers offer access to the global public voice...

Determining the Network Portion of an IP Address

Given an address and mask, you can determine the classful network, the subnetwork, and the subnetwork's broadcast number. You do so with a logical AND operation between the IP address and subnet mask. You obtain the broadcast address by taking the subnet number and making the host portion all ls. Table 7-l4 shows the logical AND operation. Notice that the AND operation is similar to multiplying bit l and bit 2 if any 0 is present, the result is 0. Table 7-14 The AND Logical Operation Table 7-14...

Route Redistribution

You configure the redistribution of routing protocols on routers that reside at the Service Provider Edge of the network. These routers exchange routes with other autonomous systems. Redistribution is also done on routers that run more than one routing protocol. Here are some reasons to do redistribution Migration from an older routing protocol to a new routing protocol. Mixed-vendor environment in which Cisco routers might be using EIGRP and other vendor routers might be using OSPF. Different...

Network Audit Tools

When performing a network audit, you have three primary sources of information Existing network management software New network management tools After gathering the existing documentation, you must obtain access to the existing management software. The client may already have CiscoWorks tools from which you can obtain hardware models and components and software versions. You can also obtain the existing router and switch configurations. The network audit should provide the following information...

EIGRP Components

EIGRP has four components that characterize it Neighbor discovery and recovery Reliable Transport Protocol (RTP) You should know the role of the EIGRP components, which are described in the following sections. EIGRP uses different modules that independently support IP, Internetwork Packet Exchange (IPX), and AppleTalk routed protocols. These modules are the logical interface between DUAL and routing protocols such as IPX RIP, AppleTalk Routing Table Maintenance Protocol (RTMP), and IGRP. The...

Static Versus Dynamic Route Assignment

Static routes are manually configured on a router. They do not react to network outages. The one exception is when the static route specifies the outbound interface If the interface goes down, the static route is removed from the routing table. Because static routes are unidirectional, they must be configured for each outgoing interface the router will use. The size of today's networks makes it impossible to manually configure and maintain all the routes in all the routers in a timely manner....

WLAN Security

WLANs provide an effective solution for hard-to-reach locations and enable mobility to a level that was previously unattainable. However, WLANs without any encryption present a security risk, because publicly available software can obtain the SSIDs. The productivity improvements with WLANs are just beginning, however. The Wired Equivalent Privacy (WEP) security protocol, used in the IEEE 802.11b standard, is considered faulty and vulnerable to numerous attacks. The 802.11b protocol is the most...

Cisco UWN Architecture

With the explosion of wireless solutions in and out of the enterprise, designers must create solutions that provide mobility and business services while maintaining network security. The Cisco Unified Wireless Network (UWN) architecture combines elements of wireless and wired networks to deliver scalable, manageable, and secure WLANs. As shown in Figure 4-2, the Cisco UWN architecture is composed of five network elements Client devices These include laptops, workstations, IP phones, PDAs, and...

Introduction

So you have worked on Cisco devices for a while, designing networks for your customers, and now you want to get certified There are several good reasons to do so. The Cisco certification program allows network analysts and engineers to demonstrate their competence in different areas and levels of networking. The prestige and respect that come with a Cisco certification will definitely help you in your career. Your clients, peers, and superiors will recognize you as an expert in networking....

Pv6 Address Allocations

The leading bits of an IPv6 address can define the IPv6 address type or other reservations. These leading bits are of variable length and are called the format prefix (FP). Table 8-2 shows the allocation of address prefixes. The IPv6 address space was delegated to IANA. You can find current IPv6 allocations at Many prefixes are still unassigned. Unspecified, loopback, IPv4-compatible Reserved for Internetwork Packet Exchange (IPX) allocation Reserved for geographic-based unicast addresses...

EIGRP Metrics

EIGRP uses the same composite metric as IGRP, but the BW term is multiplied by 256 for finer granularity. The composite metric is based on bandwidth, delay, load, and reliability. MTU is not an attribute for calculating the composite metric. EIGRP calculates the composite metric with the following formula EIGRPmetric k1 * BW + (k2 * BW) (256 - load) + k3 * delay * k5 (reliability + k4) In this formula, BW is the lowest interface bandwidth in the path, and delay is the sum of all outbound...

How This Book Is Organized

This book is divided into the following parts Part I General Network Design (Chapters 1 and 2) Part II LAN and WAN Design (Chapters 3 through 6) Part III The Internet Protocol and Routing Protocols (Chapters 7 through 12) Part IV Security, Convergence, and Network Management (Chapters 13 through 16) Part V Comprehensive Scenarios (Chapter 17) Part VI Appendixes (Appendixes A and B) The CCDA Exam Topics section describes the design topics that are covered on the CCDA exam. Before you begin...

Enterprise Wanman Architecture Comparison

Enterprise WAN MAN architectures have common characteristics that allow the network designer to compare the advantages and disadvantages of each approach. Table 6-2 compares the characteristics of Private WAN, ISP Service, SP MPLS IP VPN, and Private MPLS architectures. Table 6-2 WAN MAN Architecture Comparison Table 6-2 WAN MAN Architecture Comparison The Cisco Enterprise MAN WAN architecture includes Private WAN, ISP Service, SP MPLS IP VPN, and Private MPLS Private WAN generally consists of...

CCDA Exam Topics

Cisco lists the topics of the CCDA exam on its website at http www.cisco.com web learning le3 current_exams 640-863.html. The list provides key information about what the test covers. Table I-1 lists the CCDA exam topics and the corresponding parts in this book that cover those topics. Each part begins with a list of the topics covered. Use these references as a road map to find the exact materials you need to study to master the CCDA exam topics. Note, however, that all exam information is...

Scenario Four Answers

The current Falcon network is not scalable. It is a flat network architecture using Layer 2 links in the core with no hierarchy. It does not have core, distribution, and access layers. 2. Recommend inserting a distribution layer to create a hierarchy between the core and access layers. Use Layer 3 links instead of Layer 2 links to prevent spanning-tree loop broadcast storms. 3. All hubs need to be replaced with switches. All switches should be replaced with PoE switches to provide power to...

Hierarchical Model Examples

You can implement the hierarchical model by using either routers or switches. Figure 2-2 is an example of a switched hierarchical design in the enterprise campus. In this design, the core provides high-speed transport between the distribution layers. The building-distribution layer provides redundancy and allows policies to be applied to the building-access layer. Layer 3 links between the core and distribution switches are recommended to allow the routing protocol to take care of load...

Server Farm Module

The server-farm or data-center module provides high-speed access to servers for the campus networks. You can attach servers to switches via Gigabit Ethernet or 10 Gigabit Ethernet. Some campus deployments might need EtherChannel technology to meet traffic requirements. Figure 3-13 shows an example of a server-farm module for a small network. Servers are connected via Fast Ethernet or Fast EtherChannel. The server-farm switches connect via redundant uplink ports to the core switches. The largest...

Foundation Summary

The Foundation Summary section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on the CCDA exam, a well-prepared CCDA candidate should at a minimum know all the details in each Foundation Summary before taking the exam. Table 1-3 describes the IIN phases. Table 1-3 IIN Phases Table 1-3 describes the IIN phases. Table 1-3 IIN Phases Convergence of voice, data, and video into a single transport network....

Layer 3 to Layer 2 Mapping

Multicast-aware Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) network interface cards use the reserved IEEE 802 address 0100.5e00.0000 for multicast addresses at the MAC layer. This includes Fast Ethernet and Gigabit Ethernet. Notice that for the address, the highorder byte 0x01 has the low-order bit set to 1. This bit is the Individual Group (I G) bit. It signifies whether the address is an individual address (0) or a group address (1). Hence, for multicast addresses, this...

OSPFv3 Link State Advertisements

OSPFv3 retains the LSA types used by OSPFv2 with some modifications and introduces two new LSAs Link LSA and Intra-Area-Prefix. All LSAs use a common 20-byte header that indicates the LS type, the advertising router, and the sequence number. Figure 11-7 shows the format of the LSA header. The LS age indicates the time in seconds since the LSA was generated. The LS type indicates the function performed by this LSA. This field includes a U bit and S2 and S1 bits. When the U bit is set to 0, the...

Interactive Layer Sona

SONA is an architectural framework that guides the evolution of enterprise networks to IIN to support new IT strategies. With SONA, distributed applications and services are centrally managed over a common, unified platform. An integrated system allows access to networked applications and services from all locations with greater speed and service quality. Figure 1-1 shows the SONA framework and the offerings included at each layer. SONA networks are based on a three-layer design that...

Gigabit Ethernet 10GE Design Rules

The IEEE 802.3ae supplement to the 802.3 standard, published in August 2002, specifies the standard for 10 Gigabit Ethernet. It is defined only for full-duplex operation over optical media. Hubs or repeaters cannot be used because they operate in half-duplex mode. It allows the use of Ethernet frames over distances typically encountered in metropolitan-area networks (MAN) and WANs. Other uses include data centers, corporate backbones, and server farms. 10GE has seven physical media...

Workstationto Router Redundancy

When a workstation has traffic to send to a station that is not local, the workstation has many possible ways to discover the address of a router on its network segment, including the following ICMP Router Discovery Protocol (RDP) Global Load Balancing Protocol (GLBP) The following sections cover each of these methods. Some IP workstations send an ARP frame to find a remote station. A router running proxy ARP can respond with its data link layer address. Cisco routers run proxy ARP by default....

Do I Know This Already Quiz Rws

The purpose of the Do I Know This Already quiz is to help you decide whether you need to read the entire chapter. If you intend to read the entire chapter, you do not necessarily need to answer these questions now. The eight-question quiz, derived from the major sections in the Foundation Topics portion of the chapter, helps you determine how to spend your limited study time. Table 9-l outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that...

Pv4 Versus IPv6 Routing Protocols

With the increasing use of the IPv6 protocol, the CCDA must be prepared to design networks using IPv6 routing protocols. As IPv6 was defined, routing protocols needed to be updated to support the new IP address structure. None of the IPv4 routing protocols support IPv6 networks, and none of the IPv6 routing protocols are backward-compatible with IPv4 networks. But both protocols can coexist on the same network, each with their own routing protocol. Devices with dual stacks recognize which...

Scenario Two Big Oil and Gas

Drew is an IT director at Big Oil and Gas, a medium-sized petrochemical company based in Houston. It also has operations in the Gulf and in South America. Mr. Drew is in charge of the network infrastructure, including routers and switches. His group includes personnel who can install and configure Cisco routers and switches. The Big Oil and Gas CIO wants to begin migrating from the voice network to an IP telephony solution to reduce circuit and management costs. Existing data WAN circuits...

Strategies for Exam Preparation

The strategy you use for the CCDA test might be slightly different from strategies used by other readers, mainly based on the skills, knowledge, and experience you already have obtained. For instance, if you have attended the DESGN course, you might take a different approach than someone who learned switching via on-the-job training. Regardless of the strategy you use or your background, this book is designed to help you get to the point where you can pass the exam with the least amount of time...

Codec Standards

Codecs transform analog signals into a digital bit stream and digital signals back into analog signals. Figure 15-14 shows that an analog signal is digitized with a coder for digital transport. The decoder converts the digital signal into analog form. Each codec provides a certain quality of speech. A measure used to describe the quality of speech is the Mean Opinion Score (MOS). With MOS, a large group of listeners judges the quality of speech from 5 (best) to 1 (bad). The scores are then...

Scenario One Answers

The hospital needs to provide access to patient records, prescriptions, and information from patient rooms. 2. No cost restrictions were discussed. 3. The technical requirements are as follows WLAN access from rooms on floors 6 through 10 Redundant access to servers in the data center Fast switching between LAN segments 4. The technical constraint is as follows Servers must be located in the first floor data-center rooms. 5. Figure 17-1 shows the logical diagram of the current network. Figure...

RIPv1 Message Format

The RIPvl message format is described in RFC 1058 and is shown in Figure 10-1. The RIP messages are encapsulated using User Datagram Protocol (UDP). RIP uses the well-known UDP port 520. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 IP address (2nd route entry - up to 25) Command Describes the packet's purpose. The RFC describes five commands, two of which are obsolete and one of which is reserved. The two used commands are Request Requests all or part of the responding...

Vulnerability Scanners

Vulnerability scanners determine what potential exposures are present in the network. Passive scanning tools are used to analyze the traffic flowing on the network. Active testing injects sample traffic onto the network. General vulnerability information is published at the following links CERT CC http www.cert.org Cisco Security Here are some tools used for vulnerability scanning Nessus is designed to automate the testing and discovery of known vulnerabilities. Nessus is an open-source tool...

Dual Tier Design

The dual-tier design is recommended for branch offices of 50 to 100 users, with an additional access router in the WAN edge allowing for redundancy services. Typically two 2821 or 2851 routers are used to support the WAN, and separate access switches are used to provide LAN connectivity. The infrastructure components are dual-access routers, external Layer 2 Layer 3 switches, laptops, desktops, printers, and IP phones. Dual Frame Relay links are used to connect to the corporate offices via both...

VPN Network Design

Virtual private networks typically are deployed over some kind of shared infrastructure. VPNs are similar to tunnels in that they carry traffic over an existing IP infrastructure. VPN infrastructures include the Internet, ATM Frame Relay WANs, and point-to-point connected IP infrastructures. A disadvantage of using VPNs over public networks is that the connectivity is best-effort in nature and troubleshooting is also very difficult because you don't have visibility into the service provider's...

Catalyst 6500 Services Modules

The Catalyst 6500 switching platform supports additional security services and functionality through the use of services modules. Several modules enable firewall, IDS, SSL, and network analysis services, in addition to IPsec VPN connectivity and anomaly traffic support. Catalyst 6500 service modules include the following Firewall Services Module (FWSM) is a high-speed firewall module for use in the Cisco Catalyst 6500 and Cisco 7600 series routing platforms. Up to four FWSMs can be installed in...

BGP Attributes Weight and the BGP Decision Process

BGP is a protocol that uses route attributes to select the best path to a destination. This subsection describes BGP attributes, the use of weight to influence path selection, and the BGP decision process. BGP uses several attributes for the path-selection process. BGP uses path attributes to communicate routing policies. BGP path attributes include next hop, local preference, AS path, origin, multiexit discriminator (MED), atomic aggregate, and aggregator. Of these, the AS path is one of the...

Top Down Approach

Top-down design simply means starting your design from the top layer of the OSI model and working your way down. Top-down design adapts the network and physical infrastructure to the network application's needs. With a top-down approach, network devices and technologies are not selected until the applications' requirements are analyzed. Figure 1-3 shows a top-down structure design process. The design process begins with the applications and moves down to the network. Notice that SONA's Network...

Risk Assessment

Within network security, proper risk management is a technique used to lower risks to within acceptable levels. A well-thought-out plan for network security design implements the components included in the security policy. The security policies that an organization employs use risk assessments and cost-benefit analysis to reduce security risks. Figure 13-4 shows the three major components of risk assessment. Control refers to how you use the security policy to minimize potential risks. Severity...

Cisco Security Appliances

Cisco Security Appliances provide robust security services and protection, including IPsec VPNs and stateful packet filtering. The following is an overview of Cisco Security Appliances Adaptive Security Appliance (ASA) The ASA is a high-performance multifunction security appliance that offers a comprehensive set of services for securing network environments. The services are customized through product editions tailored for firewall, IPS, anti-X, and VPN. The ASA is a critical component of the...

PBX and PSTN Switches

Traditional switches and PBXs route voice using TDM technology and use 64-kbps circuits. The CCDA must understand some of the differences between these devices. The PBX, as its name states, is used in a private network and uses proprietary protocols. The PBX is located in the enterprise's data center. Each PBX may scale up to 1000 phones. Companies deploy PBX networks to obtain enterprise features and to prevent PSTN long-distance charges. PBXs are customer-owned voice switches. Enterprise...

Do I Know This Already Quiz Mms

The purpose of the Do I Know This Already quiz is to help you decide whether you need to read the entire chapter. If you intend to read the entire chapter, you do not necessarily need to answer these questions now. The ten-question quiz, derived from the major sections in the Foundation Topics portion of the chapter, helps you determine how to spend your limited study time. Table 16-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that...

RIPv1 Timers

The Cisco implementation of RIPv1 uses four timers RIPv1 sends its full routing table out all configured interfaces. The table is sent periodically as a broadcast (255.255.255.255) to all hosts. The update timer specifies the frequency of the periodic broadcasts. By default, the update timer is set to 30 seconds. Each route has a timeout value associated with it. The timeout gets reset every time the router receives a routing update containing the route. When the timeout value expires, the...

IPT Components

Cisco's IPT architecture divides voice system architectures into four major functional areas, as shown in Figure 15-10 Voice Enabled Infrastructure Client endpoints include the IP phones, analog and digital gateways, and digital signal processor (DSP) farms. Included here is Cisco's IP Communicator, which is the software-based IP phone that runs on a PC or laptop. Gateways are used to access PBXs, analog phones, other IP telephony deployments, or the PSTN. The Cisco Unified CallManager (CM)...

Dual Stack Backbones

In this model, all routers in the backbone are dual-stack, capable of routing both IPv4 and IPv6 packets. The IPv4 protocol stack is used between IPv4 hosts, and the IPv6 protocol stack is used between IPv6 hosts. This deployment model works for organizations with a mixture of IPv4 and IPv6 applications. Figure 8-8 shows a network with a dual-stack backbone. All the WAN routers run both IPv4 and IPv6 routing protocols. The disadvantages are that the WAN routers require dual addressing, run two...

Enterprise Data Center Infrastructure

Data centers (DC) contain different types of server technologies, including standalone servers, blade servers, mainframes, clustered servers, and virtual servers. Figure 3-14 shows the Enterprise DC. The DC access layer must provide the port density to support the servers, provide high-performance low-latency Layer 2 switching, and support dual and single connected servers. The preferred design is to contain Layer 2 to the access layer and Layer 3 on the distribution. Some solutions push Layer...

Cisco IOS Packaging

Cisco IOS packaging involves consolidating and organizing the IOS software using consistent and standardized naming across all router platforms. The four base service categories are as follows IP Base Entry-level IOS supporting IP data IP Voice Supports converged voice and data Advanced Security Security features and VPN Enterprise Base Enterprise Layer 3 protocols and IBM support In addition, three additional premium packages offer new IOS software features that focus on more complex...

Wireless LAN Standards

Wireless LAN (WLAN) applications include inside-building access, LAN extension, outside building-to-building communications, public access, and small office home office (SOHO) communications. The first standard for wireless LANs is IEEE 802.11, approved by the IEEE in 1997. The current specification is IEEE 802.11-1999, with many amendments thereafter. IEEE 802.11 implemented wireless LANs at speeds of 1 Mbps and 2 Mbps using Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread...

IP Address Subnet Design Example

This example shows subnetting for a small company. Say the company has 200 hosts and is assigned the Class C network of 195.10.1.0 24. The 200 hosts are in six different LANs. You can subnet the Class C network using a mask of 255.255.255.224. Looking at the mask in binary (11111111 11111111 11111111 11100000), the first three bytes are the network part, the first 3 bits of the fourth byte determine the subnets, and the five remaining 0 bits are for host addressing. Table 7-13 shows the...

Data Link Layer OSI Layer

This layer is concerned with the reliable transport of data across a physical link. Data at this layer is formatted into frames. Data link specifications include frame sequencing, flow control, synchronization, error notification, physical network topology, and physical addressing. This layer converts frames into bits when sending information and converts bits into frames when receiving information from the physical media. Bridges and switches operate at the data link layer. Because of the...

Routing Loop Prevention Schemes

Some routing protocols employ schemes to prevent the creation of routing loops in the network. These schemes are Split horizon with poison reverse Split horizon is a technique used by distance-vector routing protocols to prevent routing loops. Routes that are learned from a neighboring router are not sent back to that neighboring router, thus suppressing the route. If the neighbor is already closer to the destination, it already has a better path. In Figure 9-6, Routers 1, 2, and 3 learn about...

Gigabit Ethernet Design Rules

Gigabit Ethernet was first specified by two standards IEEE 802.3z-1998 and 802.3ab-1999. The IEEE 802.3z standard specifies the operation of Gigabit Ethernet over fiber and coaxial cable and introduces the Gigabit Media-Independent Interface (GMII). These standards are superseded by the latest revision of all the 802.3 standards included in IEEE 802.3-2002. The IEEE 802.3ab standard specified the operation of Gigabit Ethernet over CAT 5 UTP. Gigabit Ethernet still retains the frame formats and...

Path MTU Discovery

IPv6 does not allow packet fragmentation throughout the internetwork. Only sending hosts are allowed to fragment. Routers are not allowed to fragment packets. RFC 2460 specifies that the MTU of every link in an IPv6 must be 1280 bytes or greater. RFC 1981 recommends that nodes should implement IPv6 path MTU discovery to determine whether any paths are greater than 1280 bytes. ICMPv6 packet-too-big error messages determine the path MTU. Nodes along the path send the ICMPv6 packet-too-big message...

Enterprise Campus Module

The Enterprise Campus consists of the following submodules Figure 2-5 shows the Enterprise Campus model. The campus infrastructure consists of the campus core, building-distribution, and building-access layers. The campus core provides a high-speed switched backbone between buildings, to the server farm and to the enterprise distribution. This segment consists of redundant and fast convergence connectivity. The building-distribution layer aggregates all the closet access switches and performs...

Scenario One Pearland Hospital

Robertson, the IT director at Pearland Hospital, is responsible for managing the network. Mr. Robertson has requested your help in proposing a network solution that will meet the hospital's requirements. The hospital is growing, and the management has released funds for network improvements. The medical staff would like to be able to access medical systems using laptops from any of the patient rooms. Doctors and nurses should be able to access patient medical records, x-rays, prescriptions,...

Dense Wave Division Multiplexing

Dense Wave Division Multiplexing (DWDM) increases fiber optic's bandwidth capabilities by using different wavelengths of light called channels over the same fiber strand. It maximizes the use of the installed base of fiber used by service providers and is a critical component of optical networks. DWDM allows for service providers to increase the services offered to customers by adding new bandwidth to existing channels on the same fiber. DWDM lets a variety of devices access the network,...

Scenario Four Falcon Communications

Falcon Communications has requested an assessment of its current network infrastructure. You are given the diagram shown in Figure 17-5. The current infrastructure contains three 6500 Catalyst switches connected using Layer 2 links. Building access switches, WAN routers, Internet firewalls, the mainframe, and Windows servers all connect to the 6500 switches. Some Fast Ethernet hubs are used on the network. The IT manager mentions that they experience sporadic network outages several times...

SNMP Message Types

SNMPvl was initially defined by RFC 1157. Since then, SNMP has evolved with a second and third version, each adding new message types. The CCDA should understand each message type and the version associated with each. SNMPv1 is defined by RFC 1157. It is a simple request-and-response protocol. The NMS manager issues a request, and managed devices return responses. The date types are limited to 32-bit values. SNMPvl uses four protocol operations, with five message types to carry out the...

Pv4 Address Subnets

Subnetting plays an important part in IPv4 addressing. The subnet mask helps determine the network, subnetwork, and host part of an IP address. The network architect uses subnetting to manipulate the default mask to create subnetworks for LAN and WAN segments. These subnetworks provide enough addresses for LANs of different sizes. Point-to-point WAN links usually get a subnet mask that allows for only two hosts because only two routers are present in the point-to-point WAN link. You should...

Media Redundancy

In mission-critical applications, it is often necessary to provide redundant media. In switched networks, switches can have redundant links to each other. This redundancy is good because it minimizes downtime, but it can result in broadcasts continuously circling the network, which is called a broadcast storm. Because Cisco switches implement the IEEE 802.1d spanning-tree algorithm, you can avoid this looping in Spanning Tree Protocol (STP). The spanning-tree algorithm guarantees that only one...

Binary Numbers

The binary number system uses two digits 1 and 0. Computer systems use binary numbers. IP addresses and MAC addresses are represented by binary numbers. The number of binary 1s or 0s is the number of bits, short for binary digits. For example, 01101010 is a binary number with 8 bits. An IP address has 32 bits, and a MAC address has 48 bits. As shown in Table B-2, IPv4 addresses are usually represented in dotted-decimal format therefore, it is helpful to know how to convert between binary and...

RIPng Message Format

Figure 10-5 shows the RIPng routing message. Each route table entry (RTE) consists of the IPv6 prefix, route tag, prefix length, and metric. Figure 10-5 RIPng Update Message Format Command Indicates whether the packet is a request or response message. This field is set to 1 for a request and to 2 for a response. Version Set to 1, the first version of RIPng. IPv6 prefix The destination 128-bit IPv6 prefix. Route tag As with RIPv2, this is a method that distinguishes internal routes (learned by...

Distance Vector Routing Protocols

The first IGP routing protocols introduced were distance-vector routing protocols. They used the Bellman-Ford algorithm to build the routing tables. With distance-vector routing protocols, routes are advertised as vectors of distance and direction. The distance metric is usually router hop count. The direction is the next-hop router (IP address) toward which to forward the packet. For RIP, the maximum number of hops is 15, which can be a serious limitation, especially in large nonhierarchical...

Ground Start Signaling

Ground-start signaling is an analog signaling technique used to indicate on-hook and off-hook conditions. Ground-start is commonly used in switch-to-switch connections. The difference between ground-start and loop-start is that ground-start requires the closing of the loop at both locations. Ground-start is commonly used by PBXs. The standard way to transport voice between two telephone sets is to use tip and ring lines. Tip and ring lines are the twisted pair of wires that connect to your...

Enterprise Campus LANs

A campus LAN connects two or more buildings within a local geographic area using a high-bandwidth LAN media backbone. Usually the enterprise owns the medium (copper or fiber). High-speed switching devices minimize latency. In today's networks, Gigabit Ethernet campus backbones are the standard for new installations. In Figure 3-10, Layer 3 switches with Gigabit Ethernet media connect campus buildings. Ensure that you implement a hierarchical composite design on the campus LAN and that you...

Benefits of the Hierarchical Model

The benefits of using hierarchical models for your network design include the following After adopting hierarchical design models, many organizations report cost savings because they are no longer trying to do everything in one routing or switching platform. The model's modular nature enables appropriate use of bandwidth within each layer of the hierarchy, reducing the provisioning of bandwidth in advance of actual need. Keeping each design element simple and functionally focused facilitates...

Pilot and Prototype Tests

As soon as the design is complete and before the full implementation, it is a best practice to test the new solution. This testing can be done in one of two ways prototype or pilot. A prototype network is a subset of the full design, tested in an isolated environment. The prototype does not connect to the existing network. The benefit of using a prototype is that it allows testing of the network design before it is deployed before affecting a production network. A pilot site is an actual live...