Network management

Network management is the discipline in computing dealing with operating, managing and monitoring voice and

data networks.

Network management is often defined as consisting of five areas, using the acronym FCAPS:

Fault Management

Configuration Management

Accounting (Administration)

Performance Management

Security Management.

Fault ManagementFault management is the component of network management concerned with detecting, isolating and resolving problems. Properly implemented, fault management can keep a network running at an optimum level, provide a measure of fault tolerance and minimize downtime. A set of functions or applications designed specifically for this purpose is called a fault-management platform.

Important functions of fault management include:

Definition of thresholds for potential failure conditions.

Constant monitoring of system status and usage levels.

Continuous scanning for threats such as viruses and Trojans.

General diagnostics.

Remote control of system elements including workstations and servers from a single location.

Alarms that notify administrators and users of impending and actual malfunctions.

Tracing the locations of potential and actual malfunctions.

Automatic correction of potential problem-causing conditions.

Automatic resolution of actual malfunctions.

Detailed logging of system status and actions taken.

Configuration ManagementNetwork configuration management (NCM) is the process of organizing and maintaining information about all the components of a computer network. When a network needs repair, modification, expansion or upgrading, the administrator refers to the network configuration management database to determine the best course of action. This database contains the locations and network addresses of all hardware devices, as well as information about the programs, versions and updates installed in network computers.

Network configuration management tools can be vendor-neutral or vendor-specific. Vendor-neutral tools, by far the more common, are designed for networks containing hardware and programs from multiple suppliers. Vendor-specific tools usually work only with the products of a single company, and can offer enhanced performance in networks where that vendor dominates.

Advantages of network configuration management include:

Streamlining the processes of maintenance, repair, expansion and upgrading.

Minimizing configuration errors.

Minimizing downtime.

Optimizing network security.

Ensuring that changes made to a device or system do not adversely affect other devices or

systems.

Rolling back changes to a previous configuration if results are unsatisfactory.

Archiving the details of all network configuration changes.

Accounting Management

Accounting management is the process used to measure network utilization parameters so that individual or group users on the network can be regulated appropriately for the purposes of accounting or chargeback. Similar to performance management, the first step toward appropriate accounting management is to measure the utilization of all important network resources. Network resource utilization can be measured using the Cisco NetFlow and Cisco IP Accounting features. Analysis of the data gathered through these methods provides insight into current usage patterns.

A usage-based accounting and billing system is an essential part of any service level agreement (SLA). It provides both a practical way of defining obligations under an SLA and clear consequences for behavior outside the terms of the SLA.

Performance Management SystemsSuccessful organizations know that to win in today’s competitive marketplace they must attract, develop, and retain talented and productive employees. Winning organizations get their competitive edge from a performance management system that helps them hire talented people, place them in the right position, align their individual performance with the organization’s vision and strategic objectives, develop their abilities, and reward performance commensurate with contributions to the organization’s success. Benefits of Effective Performance Management

Improved Productivity -- Improvement in both the way people work and the outcomes they produce.

Improved Employee Morale -- Resulting from on-time performance appraisals and rewards commensurate with employee contributions.

Retention of Top Performers – Employees who feel accomplished in their work become loyal employees.

Increased Profitability – Loyal employees deliver higher levels of service that result in customer loyalty.

TCP/IP Protocol Architecture ModelThe OSI model describes idealized network communications with a family of protocols. TCP/IP does not directly correspond to this model. TCP/IP either combines several OSI layers into a single layer, or does not use certain layers at all. The following table shows the layers of the Oracle Solaris implementation of TCP/IP. The table lists the layers from the topmost layer (application) to the bottommost layer (physical network).

Table 1–2 TCP/IP Protocol Stack

OSI Ref. Layer No. 

OSI Layer Equivalent 

TCP/IP Layer 

TCP/IP Protocol Examples 

5,6,7  Application, session, presentation 

Application NFS, NIS, DNS, LDAP, telnet, ftp, rlogin, rsh, rcp, RIP, RDISC, SNMP, and others

OSI Ref. Layer No. 

OSI Layer Equivalent 

TCP/IP Layer 

TCP/IP Protocol Examples 

4  Transport   Transport TCP, UDP, SCTP 

3  Network  Internet IPv4, IPv6, ARP, ICMP 

2  Data link  Data link PPP, IEEE 802.2 

1  Physical  Physical network

Ethernet (IEEE 802.3), Token Ring, RS-232, FDDI, and others  

The table shows the TCP/IP protocol layers and the OSI model equivalents. Also shown are examples of the protocols that are available at each level of the TCP/IP protocol stack. Each system that is involved in a communication transaction runs a unique implementation of the protocol stack.

Physical Network LayerThe physical network layer specifies the characteristics of the hardware to be used for the network. For example, physical network layer specifies the physical characteristics of the communications media. The physical layer of TCP/IP describes hardware standards such as IEEE 802.3, the specification for Ethernet network media, and RS-232, the specification for standard pin connectors.

Data-Link LayerThe data-link layer identifies the network protocol type of the packet, in this instance TCP/IP. The data-link layer also provides error control and “framing.” Examples of data-link layer protocols are Ethernet IEEE 802.2 framing and Point-to-Point Protocol (PPP) framing.

Internet LayerThe Internet layer, also known as the network layer or IP layer, accepts and delivers packets for the network. This layer includes the powerful Internet Protocol (IP), the Address Resolution Protocol (ARP), and the Internet Control Message Protocol (ICMP).

IP ProtocolThe IP protocol and its associated routing protocols are possibly the most significant of the entire TCP/IP suite. IP is responsible for the following:

IP addressing – The IP addressing conventions are part of the IP protocol. Designing an IPv4 Addressing Scheme introduces IPv4 addressing and IPv6 Addressing Overview introduces IPv6 addressing.

Host-to-host communications – IP determines the path a packet must take, based on the receiving system's IP address.

Packet formatting – IP assembles packets into units that are known as datagrams. Datagrams are fully described in Internet Layer: Where Packets Are Prepared for Delivery.

Fragmentation – If a packet is too large for transmission over the network media, IP on the sending system breaks the packet into smaller fragments. IP on the receiving system then reconstructs the fragments into the original packet.

Oracle Solaris supports both IPv4 and IPv6 addressing formats, which are described in this book. To avoid confusion when addressing the Internet Protocol, one of the following conventions is used:

When the term “IP” is used in a description, the description applies to both IPv4 and IPv6. When the term “IPv4” is used in a description, the description applies only to IPv4. When the term “IPv6” is used in a description, the description applies only to IPv6.

ARP ProtocolThe Address Resolution Protocol (ARP) conceptually exists between the data-link and Internet layers. ARP assists IP in directing datagrams to the appropriate receiving system by mapping Ethernet addresses (48 bits long) to known IP addresses (32 bits long).

ICMP Protocol

The Internet Control Message Protocol (ICMP) detects and reports network error conditions. ICMP reports on the following:

Dropped packets – Packets that arrive too fast to be processed Connectivity failure – A destination system cannot be reached Redirection – Redirecting a sending system to use another router

Internet Control Message ProtocolFrom Wikipedia, the free encyclopedia

The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet Protocol Suite. It is chiefly used by

the operating systems of networked computers to send error messages indicating, for example, that a requested service is not

available or that a host or router could not be reached. ICMP can also be used to relay query messages.[1] It is assigned

protocol number 1.[2]

ICMP[3] differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems,

nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools

like ping and traceroute).

ICMP for Internet Protocol version 4 (IPv4) is also known as ICMPv4. IPv6 has a similar protocol, ICMPv6.

Transport LayerThe TCP/IP transport layer ensures that packets arrive in sequence and without error, by swapping acknowledgments of data reception, and retransmitting lost packets. This type of communication is known as end-to-end. Transport layer protocols at this level are Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Stream Control Transmission Protocol (SCTP). TCP and SCTP provide reliable, end-to-end service. UDP provides unreliable datagram service.

TCP ProtocolTCP enables applications to communicate with each other as though they were connected by a physical circuit. TCP sends data in a form that appears to be transmitted in a character-by-character fashion, rather than as discrete packets. This transmission consists of the following:

Starting point, which opens the connection Entire transmission in byte order Ending point, which closes the connection.

TCP attaches a header onto the transmitted data. This header contains many parameters that help processes on the sending system connect to peer processes on the receiving system.

TCP confirms that a packet has reached its destination by establishing an end-to-end connection between sending and receiving hosts. TCP is therefore considered a “reliable, connection-oriented” protocol.

SCTP ProtocolSCTP is a reliable, connection-oriented transport layer protocol that provides the same services to applications that are available from TCP. Moreover, SCTP can support connections between systems that have more than one address, or multihomed. The SCTP connection between sending and receiving system is called an association. Data in the association is organized in chunks. Because SCTP supports multihoming, certain applications, particularly applications used by the telecommunications industry, need to run over SCTP, rather than TCP.

UDP ProtocolUDP provides datagram delivery service. UDP does not verify connections between receiving and sending hosts. Because UDP eliminates the processes of establishing and verifying connections, applications that send small amounts of data use UDP.

Application Layer

The application layer defines standard Internet services and network applications that anyone can use. These services work with the transport layer to send and receive data. Many application layer protocols exist. The following list shows examples of application layer protocols:

Standard TCP/IP services such as the ftp, tftp, and telnet commands UNIX “r” commands, such as rlogin and rsh Name services, such as NIS and the domain name system (DNS) Directory services (LDAP) File services, such as the NFS service Simple Network Management Protocol (SNMP), which enables network management Router Discovery Server protocol (RDISC) and Routing Information Protocol (RIP) routing protocols

Standard TCP/IP Services

FTP and Anonymous FTP – The File Transfer Protocol (FTP) transfers files to and from a remote network. The protocol includes the ftpcommand and the in.ftpd daemon. FTP enables a user to specify the name of the remote host and file transfer command options on the local host's command line. The in.ftpd daemon on the remote host then handles the requests from the local host. Unlike rcp,ftp works even when the remote computer does not run a UNIX based operating system. A user must log in to the remote system to make an ftp connection, unless the remote system has been configured to allow anonymous FTP.

You can obtain an enormous amount of material from anonymous FTP servers that are connected to the Internet. Universities and other institutions set up these servers to offer software, research papers, and other information to the public domain. When you log in to this type of server, you use the login name anonymous, hence the term “anonymous FTP server.”

Using anonymous FTP and setting up anonymous FTP servers is outside the scope of this manual. However, many books, such as The Whole Internet User's Guide & Catalog, discuss anonymous FTP in detail. Instructions for using FTP are in System Administration Guide: Network Services. The ftp(1) man page describes all ftp command options that are invoked through the command interpreter. Theftpd(1M) man page describes the services that are provided by the in.ftpd daemon.

Telnet – The Telnet protocol enables terminals and terminal-oriented processes to communicate on a network that runs TCP/IP. This protocol is implemented as the telnet program on local systems and the in.telnetd daemon on remote machines. Telnet provides a user interface through which two hosts can communicate on a character-by-character or line-by-line basis. Telnet includes a set of commands that are fully documented in the telnet(1) man page.

TFTP – The Trivial File Transfer Protocol (tftp) provides functions that are similar to ftp, but the protocol does not establish ftp's interactive connection. As a result, users cannot list the contents of a directory or change directories. A user must know the full name of the file to be copied. The tftp(1)man page describes the tftp command set.

UNIX “r” CommandsThe UNIX “r” commands enable users to issue commands on their local machines that run on the remote host. These commands include the following:

rcp rlogin rsh

Instructions for using these commands are in the rcp(1), rlogin(1), and rsh(1) man pages.

Name ServicesOracle Solaris provides the following name services:

DNS – The domain name system (DNS) is the name service provided by the Internet for TCP/IP networks. DNS provides host names to the IP address service. DNS also serves as a database for mail administration. For a complete description of this service, see System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP). See also the resolver(3RESOLV) man page.

/etc files – The original host-based UNIX name system was developed for standalone UNIX machines and then adapted for network use. Many old UNIX operating systems and computers still use this system, but it is not well suited for large complex networks.

NIS – Network Information Service (NIS) was developed independently of DNS and has a slightly different focus. Whereas DNS focuses on making communication simpler by using machine names instead of numerical IP addresses, NIS focuses on making network administration more manageable by providing centralized control over a variety of

network information. NIS stores information about machine names and addresses, users, the network itself, and network services. NIS name space information is stored in NIS maps. For more information on NIS Architecture and NIS Administration, see System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).

Directory ServiceOracle Solaris supports LDAP (Lightweight Directory Access Protocol) in conjunction with the Sun Open Net Environment (Sun ONE) Directory Server, as well as other LDAP directory servers. The distinction between a name service and a directory service is in the differing extent of functionality. A directory service provides the same functionality of a naming service, but provides additional functionalities as well. See System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).

File ServicesThe NFS application layer protocol provides file services for Oracle Solaris. You can find complete information about the NFS service in System Administration Guide: Network Services.

Network AdministrationThe Simple Network Management Protocol (SNMP) enables you to view the layout of your network and the status of key machines. SNMP also enables you to obtain complex network statistics from software that is based on a graphical user interface (GUI). Many companies offer network management packages that implement SNMP.

Routing ProtocolsThe Routing Information Protocol (RIP) and the Router Discovery Server Protocol (RDISC) are two available routing protocols for TCP/IP networks. For complete lists of available routing protocols for Oracle Solaris 10, refer to Table   5–1  and Table   5–2 .

What is SNMP?

• SNMP (Simple Network Management Protocol) is a standard

produced by working groups within the IETF (Internet Engineering

Task Force). It is published as a set of RFCs.

• SNMP is more than a protocol. It is a management framework,

including an architecture, an information model, management

operations, etc.

• SNMP is the most widely used management framework today, but

many other frameworks exist. Virtually all networked devices support

SNMP.

• This presentation refers to SNMP version 1, unless stated otherwise.

We will discuss the key extensions in versions 2 and 3.

Management information base

A management information base (MIB) is a virtual database used for managing the entities in a

communications network. Most often associated with the Simple Network Management Protocol (SNMP), the

term is also used more generically in contexts such as in OSI/ISO Network management model. While intended

to refer to the complete collection of management information available on an entity, it is often used to refer to a

particular subset, more correctly referred to as MIB-module.

Objects in the MIB are defined using a subset of Abstract Syntax Notation One (ASN.1) called "Structure of

Management Information Version 2 (SMIv2)" RFC 2578.The software that performs the parsing is a MIB

compiler.

The database is hierarchical (tree-structured) and entries are addressed through object

identifiers. Internet documentation RFCs discuss MIBs, notably RFC 1155, "Structure and Identification of

Management Information for TCP/IP based internets", and its two companions, RFC 1213, "Management

Information Base for Network Management of TCP/IP-based internets", and RFC 1157, "A Simple Network

Management Protocol".

A management information base (MIB) is a formal description of a set of network objects that can be managed using the Simple Network Management Protocol (SNMP). The format of the MIB is defined as part of the SNMP. (All other MIBs are extensions of this basic management information base.) MIB-I refers to the initial MIB definition; MIB-II refers to the current definition. SNMPv2 includes MIB-II and adds some new objects.

Address Resolution ProtocolShort for Address Resolution Protocol, a network layer protocol used to convert an IP address into a physical address (called a DLC address), such as an Ethernet address. A host wishing to obtain a physical addressbroadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address.There is also Reverse ARP (RARP) which can be used by a host to discover its IP address. In this case, the host broadcasts its physical address and a RARP server replies with the host's IP address.

Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network

layer addresses into link layer addresses, a critical function in multiple-access networks. ARP was

defined byRFC 826 in 1982.[1] It is Internet Standard STD 37. It is also the name of the program for

manipulating these addresses in most operating systems.

subnet maskA mask used to determine what subnet an IP address belongs to. An IP address has two components, the network address and the host address. For example, consider the IP address 150.215.017.009. Assuming this is part of a Class B network, the first two numbers (150.215) represent the Class B network address, and the second two numbers (017.009) identify a particular host on this network.Subnetting enables the network administrator to further divide the host part of the address into two or more subnets. In this case, a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format. The full address is:10010110.11010111.00010001.00001001The Class B network part is:10010110.11010111and the host address is00010001.00001001If this network is divided into 14 subnets, however, then the first 4 bits of the host address (0001) are reserved for identifying the subnet.

A subnet allows the flow of network traffic between hosts to be segregated based on a network configuration. By organizing hosts into logical groups, subnetting can improve network security and performance.

Subnet Mask

Perhaps the most recognizable aspect of subnetting is the subnet mask. Like IP addresses, a subnet mask contains four bytes (32 bits) and is often written using the same "dotted-decimal" notation. For example, a very common subnet mask in its binary representation

11111111 11111111 11111111 00000000

is typically shown in the equivalent, more readable form

255.255.255.0

DMI (Desktop Management Interface)

Desktop Management Interface (DMI) is an industry framework for managing and keeping track of hardware and software components in a system of personal computers from a central location. DMI was created by the Desktop Management Task Force (DMTF) to automate system management and is particularly beneficial in a network computing environment where dozens or more computers are managed. DMI is hardware and operating system-independent, independent of specific management protocol, easy for vendors to adopt, mappable to existing management protocols such as the Simple Network Management Protocol (SNMP), and used on network and non-network computers. DMI consists of four components:

Management Information Format (MIF): An MIF is a text file that contains specific information

about the hardware and software being used on a computer. An MIF file consists of one or more

groups containing attributes, which describe each component. By default, each MIF file contains

the standard component ID group.

This group contains the product name, version, serial number, and the time and date of the last

installation. The ID number is assigned based on when the component was installed in relation

to other components. Manufacturers can create their own MIFs specific to a component. For

example, a manufacturer might write an MIF file for a fax/modem that contains two groups: a

fax group and a modem group. Some group attributes include warranty information, support

phone numbers, and any errors encountered. This information is then sent to an MIF database.

Service layer: The service layer is memory-resident code that acts as a mediator for the

management interface and the component interface and allows management and component

software to access MIF files in the MIF database. The service layer is available as an operating

system add-on and is a shared resource for all programs. Because the service layer must run all

the time, it is designed not to use a lot of memory. The service layer also includes a common

interface called the local agent, which is used to manage individual components.

Component interface (CI): The CI is an application program interface (API) that sends status

information to the appropriate MIF file via the service layer. Commands include the Get and Set

command that modifies the MIF as needed and the Event command that notifies management

software of critical events.

Management interface (MI): The management software communicates with the service layer

using the MI application program interface. The MI allows administrators to issue the Get and

Set command and the List command that lists all the DMI-manageable devices.

Internet Group Management ProtocolThe Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and

adjacent routers on IP networks to establish multicast group memberships.

IGMP is an integral part of the IP multicast specification. It is analogous

to ICMP for unicast connections. IGMP can be used for online streaming video and gaming, and

allows more efficient use of resources when supporting these types of applications.

IGMP is used on IPv4 networks. Multicast management on IPv6 networks is handled by Multicast

Listener Discovery (MLD) which uses ICMPv6 messaging contrary to IGMP's bare IP encapsulation.

A network designed to deliver a multicast service using IGMP might use this basic architecture:

IGMP is used between the client computer and a local multicast router. Switches featuring IGMP

snooping derive useful information by observing these IGMP transactions. Protocol Independent

Multicast (PIM) is then used between the local and remote multicast routers, to direct multicast traffic

from the multicast server to many multicast clients.

IGMP operates above the network layer, though it does not actually act as a transport protocol.]

Routing Information ProtocolThe Routing Information Protocol (RIP) is a distance-vector routing protocol, which employs

the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number

of hops allowed in a path from the source to a destination. The maximum number of hops allowed for

RIP is 15. This hop limit, however, also limits the size of networks that RIP can support. A hop count

of 16 is considered an infinite distance and used to deprecate inaccessible, inoperable, or otherwise

undesirable routes in the selection process.

RIP implements the split horizon, route poisoning and holddown mechanisms to prevent incorrect

routing information from being propagated. These are some of the stability features of RIP. It is also

possible to use the so called RMTI[1] (Routing Information Protocol with Metric-

based Topology Investigation) algorithm to cope with the count-to-infinity problem. With its help, it is

possible to detect every possible loop with a very small computation effort.

Limitations

Without using RMTI, Hop count can not exceed 15, in the case that it exceeds this limitation, it will be considered invalid.

Most RIP networks are flat. There is no concept of areas or boundaries in RIP networks.

Variable Length Subnet Masks were not supported by RIP version 1.

Without using RMTI, RIP has slow convergence and count to infinity problems

Virtual private networkA virtual private network (VPN) is a network that uses primarily public telecommunication

infrastructure, such as the Internet, to provide remote offices or traveling users access to a central

organizational network.

VPNs typically require remote users of the network to be authenticated, and often secure data with

encryption technologies to prevent disclosure of private information to unauthorized parties.

VPNs may serve any network functionality that is found on any network, such as sharing of data and

access to network resources, printers, databases, websites, etc. A VPN user typically experiences the

central network in a manner that is identical to being connected directly to the central network. VPN

technology via the public Internet has replaced the need to requisition and maintain expensive

dedicated leased-line telecommunication circuits once typical in wide-area network installations.

(Desktop Management Interface) The first desktop management standard from the DMTF. Enabling PCs to be monitored from a central console, it was superseded by the DMTF's Common Information Model (see CIM).

The Management Information File (MIF)

When a query is made to a DMI-enabled device, the memory-resident DMI agent sends back data such as model ID, serial number, memory and port addresses in a management information file (MIF). It can also extract data from memory to provide a current status.

Support for SNMP

DMI can co-exist with SNMP. A single machine can serve as a proxy agent to service an entire LAN segment of DMI machines. When SNMP queries arrive, it can transfer the data from the MIF into the SNMP's MIB (management information base). See CIM, SNMP, WBEM and DMTF.

What is the Cisco Discovery Protocol (CDP)?

CDP is a Cisco proprietary protocol that runs on all Cisco IOS-enabled devices. It is used to gather

information about directly connected neighboring devices. CDP operates at Layer 2 of the OSI model

and is media-independent. With CDP, you can tell the hardware type, device identifier, address list,

software version, and active interfaces on neighboring Cisco devices. CDP is enabled by default on all

Cisco equipment. It uses a nonroutable SNAP frame to communicate between devices.

Note: Because CDP is media-independent it can operate over most media types. The only media

types CDP cannot operate over are X.25, because it doesn't support SNAP encapsulation, and Frame

Relay point-to-multipoint interfaces.

What are three reasons to disable CDP?

Three reasons to disable CDP are as follows:

. To save network bandwidth by not exchanging CDP frames.

. If you are connecting to non-Cisco devices.

. Security. CDP broadcasts information about the device every 60 seconds. Sniffers and other devices

can view these broadcasts to discover information about your network.

How do you disable CDP on Cisco routers?

Two commands disable CDP on a Cisco router. To disable CDP on the entire device, use the no cdp

run global command: 

RouterB(config)#no cdp run

To disable CDP on an interface only, use the no cdp enable interface command: 

RouterB(config)#int e0

RouterB(config-if)#no cdp enable

This disables CDP on Ethernet interface 0.

What does the show CDP command display?

The show CDP command displays global CDP information about the device. It tells you when the

device will send CDP packets and the CDP holdtime: 

RouterB#show cdp

Global CDP information: 

Sending CDP packets every 60 seconds 

Sending a holdtime value of 180 seconds

Note: For the CCNA test, remember that the default time a device will send out CDP information is 60

seconds and the default holdtime is 180 seconds. 

On a Cisco router, what does the show cdp neighbors command display?

The show cdp neighbors command displays the following:

· Device ID (name of the device)

· The local interface (local outgoing port)

· The holdtime displayed in seconds

· The device's capability code (this tells you if the device is a router, switch, or repeater)

· Hardware platform of the neighboring device (what type of Cisco device it is and the model)

· Port ID of the neighboring device (remote port)

RouterB#show cdp neighbors

Capability Codes:

R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID

RouterA Ser 0 146 R 2505 Ser 0

What does the show cdp neighbors detail command display?

The show cdp neighbors detail and show cdp entry * commands show the same output. They both

display the following:

· Device ID (host name) of the remote neighbor

· Layer 3 address of the remote device (if the device has more than one Layer 3 address on its

interface, only the primary address is shown)

· Device platform and capabilities· Local interface and outgoing port ID

· Remote device holdtime in seconds

· IOS type and version

RouterB#show cdp neighbors detail

-------------------------

Device ID: RouterA

Entry address(es):

IP address: 192.168.2.1

Platform: cisco 2505, Capabilities: Router

Interface: Serial1, Port ID (outgoing port): Serial1

Holdtime : 164 sec Version :Cisco Internetwork Operating System Software

IOS (tm) 2500 Software (C2500-D-L), Version 12.0(13), RELEASE SOFTWARE

(fc1)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Wed 06-Sep-00 01:08 by Linda

What does the show cdp traffic command display?

The show cdp traffic command displays information about interface traffic. This includes the number

of CDP packets sent and received and CDP errors:

RouterB#show cdp traffic

CDP counters :

Packets output: 105, Input: 103

Hdr syntax: 0, Chksum error: 0, Encaps failed:

No memory: 0, Invalid packet: 0, Fragmented: 0

What does the show cdp interface command display?

The show cdp interface command displays the status of CDP on all interfaces on your device:

RouterB#show cdp interface

Ethernet0 is up, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds Holdtime is 180 seconds

Serial0 is up, line protocol is up

Encapsulation HDLC

Sending CDP packets every 60 seconds Holdtime is 180 seconds

Serial1 is up, line protocol is up

Encapsulation HDLC

Sending CDP packets every 60 seconds Holdtime is 180 seconds

What Cisco IOS router command can you use to see a neighbor router's IP address?

To see a neighbor router's IP address, you must use the show cdp neighbor detail or show cdp entry *

user mode or EXEC command. (This one will probably be on the exam)

What IOS command do you use to view the active outbound telnet sessions for the current user on a

Cisco router?

The show sessions command displays the active outbound telnet sessions from that particular user

on your router.

RouterA#show sessions

Conn Host Address Byte Idle Conn Name

* 1 192.168.1.2 192.168.1.2 0 0 192.168.1.2

What key sequence do you use to suspend a Telnet session on a remote system and return to your

local router?

To suspend a Telnet session, press Ctrl-Shift-6, and then press X.

How do you end a remote Telnet session on a Cisco router?

To end a Telnet session, use the exit or logout command while you're on the remote device:

RouterB>exit

[Connection to 192.168.1.2 closed by foreign host]

RouterA#

Upon using the ping EXEC command, you receive one of the following responses:

· .

· !

· ?

· C

· U

· I

What does each of these responses mean?

. = Each period indicates that the network server timed out while waiting for a reply.

! =Each exclamation point indicates the receipt of a reply.

? =Unknown packet type.

C =A congestion experienced packet was received.

U =A destination unreachable error PDU was received.

I = The user interrupted the test.

What is the trace EXEC command used for?

RouterA#trace 192.168.2.2

Type escape sequence to abort.

Tracing the route to 192.168.2.2

1 192.168.2.2 16 msec 16 msec *

Note: If trace responds with a * it means the probe timed out. If it responds with a ? it means it

received an unknown packet type.

What are the two ways in which a Cisco router resolves host names to IP addresses?

A Cisco router resolves host names using either a host table on each router or a DNS server.

What is the main purpose of RAM on a Cisco router?

On most Cisco routers, the IOS is loaded into RAM, as well as the running configuration. It is also

used to hold routing tables and packet buffers.

What is the function of ROM on a Cisco router?

On a Cisco router, ROM is used to start and maintain the router.

What is Flash memory used for on a Cisco router?

Flash memory is used to store the Cisco IOS software image and, if there is room, multiple

configuration files or multiple IOS files. On some routers (the 2500 series), it is also used to run the

IOS.

What is the function of NVRAM on a Cisco router?

Nonvolatile Random-Access Memory (NVRAM) is used to hold the saved router configuration. This

configuration is not lost when the router is turned off or reloaded.

What is the main purpose of the configuration register on a Cisco router?

The configuration register's main purpose is to control how the router boots up. It is a 16-bit software

register that by default is set to load the Cisco IOS from Flash memory and to look for and load the

startup-config file from NVRAM.

What Cisco IOS command would you use to view the current configuration register value?

The show version command is used to display the router's current configuration register:

RouterA#show version

Cisco Internetwork Operating System SoftwareIOS (tm) 2500 Software (C2500-D-L),

Version 12.0(13), RELEASE SOFTWARE (fc1)Copyright (c) 1986-2000 by cisco Systems,

Inc.Compiled Wed 06-Sep-00 01:08 by lindaImage text-base: 0x030388F8, data-base: 0x00001000

Configuration register is 0x2102

How do you change the configuration register on a Cisco router?

To change the configuration register on a Cisco router, use the config-register global command.

What Cisco IOS command displays the contents of Flash memory?

The show flash command displays the contents of Flash memory. This includes the images stored in

Flash memory, the images' names, bytes used in Flash memory, bytes available, and the total

amount of Flash memory on your router:

RouterA#show flash

System flash directory:File Length Name/status

1 6897716 c2500-d-l.120-13.bin[6897780 bytes used, 1490828 available, 8388608 total]8192K bytes

of processor board System flash (Read ONLY)

What IOS command would you use to copy the running configuration on a router to a TFTP server? 

To copy the running configuration to a TFTP server, use the copy running-config tftp privileged EXEC

command:

RouterB#copy run tftp

Address or name of remote host []? 192.168.0.2

Destination filename [routerb-confg]?

!!

780 bytes copied in 6.900 secs (130 bytes/sec)

This gives you a backup of your running config on a TFTP server.

How do you erase the router's configuration and bring it back to the factory default?

The erase startup-config privileged EXEC command erases your router's configuration, thus bringing

it back to its factory defaults:

RouterB#erase startup-config

Erasing the nvram filesystem will remove all files! Continue? [confirm]

[OK]Erase of nvram: complete

Note: In order to complete the process, you need to reload the router. An older IOS command that

you can use to accomplish the same results is write erase.

How do you restore a configuration file from a TFTP server into your Cisco router's RAM?

The copy tftp running-config privileged EXEC command merges the saved and running configuration

into your router's RAM, so any commands not explicitly change or removed will remain in the running

configuration.

RouterB#copy tftp running-config

Address or name of remote host []? 192.168.0.2

Source filename []? routerb-confg

Destination filename [running-config]?

Accessing tftp://192.168.0.2/routerb-confg...

Loading routerb-confg from 192.168.0.2 (via Ethernet0):

!

[OK - 780/1024 bytes] 780 bytes copied in 4.12 secs (195 bytes/sec)

RouterB# 01:40:46: %SYS-5-CONFIG: Configured from tftp://192.168.0.2/routerb-confg

How do you back up a Cisco router IOS?

To back up the current IOS image on your router, use the copy flash tftp privileged EXEC mode

command:

RouterB#copy flash tftp

Source filename [routerb-flash]? flash:c2500-d-l.120-13.bin

Address or name of remote host []? 192.168.0.2

Destination filename [c2500-d-l.120-13.bin]?

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!6897716 bytes copied in 90.856 secs

(76641 bytes/sec)

How do you upgrade or restore the Cisco router IOS?

To upgrade or restore the Cisco router IOS, use the copy tftp flash privileged EXEC mode command.

How you make a Cisco router a TFTP server?

To configure a Cisco router as a TFTP server, use the tftp-server global configuration command.

What is the boot sequence of a Cisco router?

The boot sequence of a router is as follows:

hardware /power on

load run bootstrapfind the IOS software

load the softwarefind the config (default NVRAM)

load the configuration (startup-config) into RAM

Run the IOS

What can you configure on a router in setup mode?

ip addresses

routed protocols

enable password

Important Config Register Notes:

2100 manual boot rommon>

2101 boot from ROM

2102 normal/password recovery

2105 boot system command - config-register NVRAM

2142 bypass NVRAM

ctrl-break = ROM monitor mode

router(config)#boot system flash ios filename

router(config)#boot system tftp filename ip address

router(config)#boot system ROM

Note the router prompt for boot commands. Copy commands = router#