Chapter 3. Initial Configuration
The first time you configure an IOS-based router, you will probably use the IOS Setup facility. We are going to start from the time you take your router out of the box; then we will walk through using the Setup facility to create an internetwork of two routers.
Our steps for initial configuration are as follows:
We'll cover each step in the next few sections.
If we are going to configure a router, we should know a little about what is inside it and what we are configuring.
Just like any other computer, a Cisco router that runs IOS has a Central Processing Unit (CPU). The CPU, or processor, varies by router series and model. Two examples of processors that Cisco uses are the Motorola 68030 and the Orion/R4600.
A router's processor performs work required to process packets such as maintaining all of the tables necessary to route and bridge and making routing decisions. The rate at which a router can process packets depends a lot on the type of processor the router has.
All computers have memory of some type. Cisco routers have four main types of memory:
Of each of these types, RAM is the only one that loses its contents when the router is booted or power-cycled. The following sections briefly describe the primary purpose of each memory type on Cisco routers.
ROM is where a router's bootstrap software is normally stored. The bootstrap software is the first software that runs; it has the responsibility of getting the router going.
Some routers have a full IOS stored in ROM for use in emergencies when another source of IOS is not available.
ROM is generally on a chip, or multiple chips, on the processor board of a router.
Flash memory's primary purpose is to store the IOS software that the router is to run. If a router has flash memory, then flash memory is the default location of the IOS software used to boot the router. With enough flash memory, multiple IOS images can be stored to provide multiple boot options.
Cisco's high-end routers, like those in the 7500 series, have two kinds of flash memory: system flash and boot flash. The IOS image is stored in system flash, and the bootstrap software is stored in boot flash.
Flash memory is either on a processor board SIMM or on a PCMCIA card
RAM is used for too many things to list, but two of the things are IOS system tables and buffers. The IOS uses RAM for all of its normal, operational storage requirements.
The primary purpose of NVRAM is to store the configuration that the IOS reads when a router boots. This configuration is called the startup configuration. See Section 3.1.6.
All routers have interfaces. Some of the interface types available on Cisco routers are listed in Section 2.3. On IOS-based routers, interfaces are named and numbered. The full name of an interface consists of its type designation and at least one number. Numbering starts with zero (0).
On those routers with fixed interfaces (most of the 2500 series) or with modular interfaces that cannot be changed without turning off the router (the 4700), the full name of an interface has one number, and interfaces are numbered according to their physical order in the router. For example, Ethernet0 is the name of the first Ethernet interface, and Serial2 is the name of the third serial interface.
On routers that support Online Insertion and Removal (OIR), or the capability to change the physical interface configuration (pull cards) while the router is still running, the full name of an interface has at least two numbers separated by a forward slash (/). The first number is a slot number where an interface processor card is installed, and the second number is a port number on the interface processor. For example, on a 7507 router, Ethernet5/0 is the name of the first Ethernet interface in slot five of the router, assuming that slot five had an Ethernet interface processor installed in it.
In the case of a 7500 series router with a Versatile Interface Processor (VIP) installed, the name of an interface on a VIP includes three numbers separated by forward slashes (/). The form of the interface number is slot/port adapter/port. For example, Ethernet4/0/1 is the name of the second Ethernet interface on the first port adapter in slot 4.
If this interface numbering stuff sounds confusing, don't worry about it for now. We will see later how to get the router to tell us the full names of all of its interfaces.
All Cisco routers have a console port on the back of the router. The console port provides an EIA/TIA-232 (formerly called RS-232) asynchronous serial connection that allows us to communicate with the router. The type of physical connection to the console port depends on the model of router. Some routers use a DB25 Female (DB25F) connector, and some use a RJ45 connector. See Figure 3-1 for a list of the connector types for the major series of Cisco routers.
<<<Figure 3-1 Cisco Router Console Connectors>>>
As a general rule, the smaller routers have a RJ45 console connector, and the larger routers have a DB25 console connector.
Most Cisco routers have an auxiliary port. Like the console port, it provides an EIA/TIA-232 asynchronous serial connection that allows us to communicate with a router. The auxiliary port is most often used for the connection of a modem for out-of-band router management. An out-of-band path does not carry routed packets; it is primarily used to access a router when a network path or circuit fails.
There are two types of IOS configurations:
Both are displayed to us in ASCII text format; therefore, they are easy to read and manipulate. A router can have only one of each type.
The running configuration is sometimes called the active configuration. The running configuration resides in RAM, and it contains the IOS configuration commands that are currently active on a router. When we configure IOS, we are changing a router's running configuration.
The startup configuration resides in NVRAM, and it contains the IOS configuration commands that are supposed to be executed when a router boots. The commands in the startup configuration essentially become the running configuration.
The startup configuration is sometimes called the backup configuration because after we make and verify running configuration changes, we normally copy the running configuration to NVRAM so our changes are backed up and available the next time the router boots.
An IOS process is a software task that is running on the router and performing some function. For example, the routing of IP packets is done with a process; the routing of AppleTalk packets is done with another process. Other examples of IOS processes are routing protocols and memory allocation routines. When we configure IOS by putting commands into the configuration files, we are essentially controlling the behavior of the processes that make up IOS. All of these processes run simultaneously on a router. The number and type of processes we can run on a router are limited by the router's CPU speed and RAM amount, just like the number of programs we can run on a PC is limited by the type of CPU and the amount of RAM it has.
Before building anything, we must develop a plan. The plan should be documented, sort of like a blueprint, so we can reference it during the implementation of the plan. When modifying an existing internetwork or building a new internetwork, a graphical representation of the layout and configuration of the internetwork comes in handy. To illustrate router configuration, we are going to be building a small internetwork. Figure 3-2 shows the basic infrastructure of the internetwork we will build.
<<<J107 - Figure 3-2 Initial Configuration Internetwork Infrastructure>>>
Throughout most of this book, Cisco 2520 routers will be used in the configuration examples; occasionally another model of Cisco router will be used to show a different view. Our two 2520's are connected to each other with a T1 leased line. A T1 is a point-to-point WAN with a bandwidth of 1.544 Megabits per second (Mbps). Each of the routers has an Ethernet LAN with a bandwidth of 10 Mbps.
Since we are starting from scratch, we will configure both routers. The following are some of the things that we must know about a new router before its initial configuration:
Knowing and documenting each of these items will make the configuration of a new router easier.
Each router should have a unique host name to identify itself. The name should be descriptive; putting the router's location in the name is a common practice.
The name you select can be just about anything you want; however, here are some guidelines from RFC 1035. A router's host name should be no longer than 63 characters, and it can contain letters, numeric digits, and hyphens. The name should start with a letter, but it can end with either a letter or a numeric digit.
By default, IOS will put the name (up to 29 characters of it) into the IOS command line prompt.
In our example routers, serial interfaces are used to connect to the T1, and Ethernet interfaces are used to connect to 10 Mbps Ethernet LAN's.
We need to specify which interfaces we will use to connect to each network. To specify interfaces, we must know what interfaces are available on the router. The Cisco 2520 has one Ethernet interface, two fast serial interfaces, two low-speed serial interfaces, and one ISDN BRI interface. The IOS sees both fast and low-speed serial interfaces as just serial interfaces; therefore, we can say that the 2520 has four serial interfaces. Figure 3-3 shows the names of our routers and the interfaces that will be configured on each router.
<<<J108 - Figure 3-3 Initial Configuration Router Names and Interfaces>>>
The router names are to be Dallas and FortWorth. On Dallas, the Ethernet0 and Serial1 interfaces will be used. On FortWorth, the Ethernet0 and Serial0 interfaces will be used. We could have connected the Dallas Serial0 to the FortWorth Serial0, but we chose to connect the Dallas Serial1 to the FortWorth Serial0 for this discussion.
As was covered in Section 2.2.2, there are two major classes of network protocols: routed and routing. We need both.
The routed protocols that we need are determined by the type of hosts on our internetwork, their operating systems, and their configured protocols. The routed protocols that can be configured on a router are determined by the its IOS Feature Set. For example, if your router is running the IP Feature Set, you can start only the IP protocol; if your router has the Enterprise Feature Set, you can start just about any protocol you want.
Our routers are running the IOS Enterprise Feature Set. Let us assume for now that that our new network will have the following types of hosts:
We will build our first internetwork by configuring the IP, IPX, and AppleTalk protocols on the routers.
For each routed protocol, there should be an associated routing protocol running on all of the routers.
To make the initial configuration a little simpler, we are going to run the following routing protocols:
IPX RIP is the default routing protocol for IPX, and RTMP is the default routing protocol for AppleTalk. In other words, when we configure IPX on an interface, IPX RIP also starts on the interface, and when we configure AppleTalk on an interface, RTMP also starts on the interface.
For IP, there is no default routing protocol; therefore, we must manually select one. We will start the simplest IP routing protocol, RIP.
Since we are going to initially configure three routed protocols, we need to assign addresses for each of the protocols for each of the routers' interfaces. The specifics of what each protocol requires for address configuration will be covered in detail on the protocol configuration sections later; however, for now, here is a basic overview of what we need.
We need an IP network, or subnet, address for each of our networks. We have three networks; therefore, we need to choose three network addresses and a network mask for each. The three network are the Dallas Ethernet LAN, the FortWorth Ethernet LAN, and the WAN between Dallas and FortWorth. For each interface, we should select an IP host address that begins with the chosen network address, for the network to which the interface is connected, and ends with a unique node address. The format of an IP address and its mask is called dotted decimal; dotted-decimal format consists of four decimal numbers between 0 and 255 separated by dots (".").
We need an IPX network number for each of our networks. Each network needs a unique IPX network number. The node portion of an IPX host address is automatically assigned when the network number is configured on an interface. The IPX network number is written in hexadecimal (hex) and has from one to eight hex digits.
We need an AppleTalk cable range and zone name for each of the networks. Each network needs a unique cable range which consists of two decimal numbers, the second being larger than the first. The node portion of an AppleTalk host address is selected dynamically when the cable range and zone name are configured on an interface. An AppleTalk zone is a logical group of AppleTalk networks. Each zone has a name that is configured on each of the interfaces that are connected to the zone's networks.
For each of the routed protocols briefly described above, each interface connected to a network must have the same network address assigned to it. For example, the Dallas Serial1 interface and the FortWorth Serial0 interface are both connected to the same network; therefore, they must have the same network address.
With these addressing principles in mind, the network addresses selected for our internetwork are shown in Figure 3-4.
<<<J109 - Figure 3-4 Initial Configuration Internetwork Network Addresses>>>
Using our network addresses, we can assign addresses for the interfaces we are going to use on our routers. Figure 3-5 shows the interface information we will need during the initial configuration of each router.
<<<Figure 3-5 Initial Configuration Interface Information>>>
This table will make our routers' initial configuration faster because the table can be referenced during the internetwork implementation.
For initial configuration, we need three passwords:
All IOS passwords are case sensitive, and they can contain any combination of uppercase and lowercase alphanumeric characters (letters, numeric digits, punctuation marks) and spaces; however, a space cannot be the first character in a password. The maximum length of an IOS password is 25 characters. The use of each of the IOS passwords will be described in Chapter 6.
The passwords we will use during IOS configuration are as follows:
Passwords should contain both letters and numeric digits; they should not contain words found in the dictionary; and they should not be easily guessed. The passwords selected here violate all of these guidelines; please do not use them in a production network.
With all of this planning, we still have not touched a router. The next section will describe the connection to the router so we can proceed with our implementation.
To access and configure IOS on a new router, we must communicate with the router through its console port. Connecting a console terminal to the router's console port enables communication with the router. The terminal can be either a non-intelligent, ASCII terminal, like an old VT100, or a computer, like your Personal Computer (PC). If we are using a PC as a terminal, we have to run terminal emulation software on the PC. Using the terminal's keyboard, we are able to type commands for IOS to execute.
Most people use a PC as their terminal to do IOS configuration. PC's usually have at least two serial ports; they are called COM1 and COM2. The serial port connectors are normally DB9 Male (DB9M) connectors, but some PC's serial ports use a DB25 Male (DB25M) connector.
The connection between the console port and the terminal is simply a serial cable. See Figure 3-1 for the console cable types needed for the two console port connector types.
A RJ45 connector looks like the phone connector in your home, only wider. The phone connector (the little tabbed connector on the end of the your phone cable that plugs into your phone jack) has four wires, and an RJ45 connector has eight.
A rollover cable looks like the cable between your phone and your wall phone jack, only wider. It's called a rollover cable because its wires are reversed, rolled over, from one end to the other.
For those routers that have a RJ45 console port, Cisco normally provides the rollover cable and at least one adapter in the router shipment box. The adapter allows the connection of the RJ45 plug to the serial port on your terminal. The adapter has a RJ45 jack for the rollover cable's RJ45 plug and a DB9 Female (DB9F) or DB25F connector for your terminal.
If your terminal has a DB9M connector for its serial port, use the RJ45-to-DB9F adapter. Plug one end of the rollover cable into the router's console port. The router's console port will be labeled as Console or an abbreviation of Console. Plug the other end of the rollover cable into the RJ45 jack on the adapter. Then connect the adapter's DB9F connector to your terminal's serial port.
If your terminal has a DB25M connector for its serial port, use the RJ45-to-DB25F adapter. Plug one end of the rollover cable into the router's console port. Plug the other end of the rollover cable into the RJ45 jack on the adapter. Then connect the adapter's DB25F connector to your terminal's serial port.
For those routers that have a DB25F console connector, you will have to provide your own cable. The cable should have a DB25M connector on one end and the appropriate connector on the other end for connection to your terminal's serial port (DB9F or DB25F). The cable should be configured to be straight through.
Plug the DB25M end of the straight-through serial cable into the router's console port, and plug the other end into your terminal's serial port.
As has already been mentioned, if the terminal to be used for IOS configuration is a PC, we will have to run terminal emulation software to allow us to type IOS commands and see IOS information.
Terminal emulation software is readily available from software stores and shareware web sites. The odds are good that your PC already has terminal emulation software installed on it.
Some examples of terminal emulation software are HyperTerminal by Hilgraeve, Procomm by DataStorm Technologies, and Kermit. Usually, availability and personal preference are the deciding factors in the choice of a terminal emulator.
Start the terminal emulation software on your PC. If you are using a non-intelligent, ASCII terminal for console communication, there is no need to run special software.
The default speed of a Cisco router's console port is 9600 baud. If you configure your terminal to run at 9600 baud, 8 data bits, no parity, and 2 stop bits (9600-8N2), you should be able to communicate with the router through the console port. (Sometimes using just 1 stop bit, instead of 2, works, also.)
Plug your female end of the router's power cable into the router's power connector on the back of the router. Plug the male end of the power cable into an appropriate power outlet.
All IOS-based Cisco routers except the 1000 series have a power switch on the back of the router. If the router has a power switch, set it to the ON (1) position. The cooling fans inside the router should immediately come on and be audible.
For specific instructions on installing and turning on your particular router, please refer to the "Hardware Installation Guide" or "Installation and Configuration Guide" for your router.
Now we are going to walk through the normal boot sequence of a new router.
The first software that runs on the router is called the bootstrap software. Every computer has bootstrap software, and, or course, a router is just a special-purpose computer. The initial software is called the bootstrap because it is said to pull a computer up by its bootstraps. The bootstrap software runs a Power-On Self-Test (POST) and then locates a boot device that contains a valid copy of IOS, the operating system. The boot device is normally system flash memory.
Within a few seconds after we turn on a router, a bootstrap message is sent to the console. The beginning of the bootstrap message from one of our 2520's, Dallas, is shown in Figure 3-6.
<<<Figure 3-6 Bootstrap Message on Dallas>>>
The bootstrap message indicates that the bootstrap software has been located and started. Bootstrap software can be in one of two places on a router: Read-Only Memory (ROM) or boot flash. On a 2500-series router like this one, the bootstrap software is in ROM.
The message states the bootstrap software version number (Line 1) and the amount of main memory in the router (Line 3). The 2520's bootstrap message shows that the 2520's bootstrap software is version 11.0(10c), and the 2520 has 6 MegaBytes (MB) of main memory. Main memory is the Random-Access Memory (RAM) used for IOS operations; it is also called system RAM or system memory. System RAM is allocated from the total amount of RAM at boot time.
Since the bootstrap software has the responsibility of finding a copy of IOS to load and run so the router can be operational, the bootstrap software checks for any special boot instructions in Non-Volatile RAM (NVRAM). NVRAM normally contains the configuration that an IOS-based router loads when it starts IOS; however, since the routers being used in this example are new, NVRAM is empty (Figure 3-6, Line 5). Under normal conditions, the bootstrap software will attempt to find an IOS image in system flash.
In our example, the bootstrap locates a copy of IOS in system flash. The message logged to our 2520's console upon locating and starting IOS is shown in Figure 3-7.
<<<Figure 3-7 IOS Boot Message on Dallas>>>
At the beginning of the logged message, we see that the IOS software is Version 11.3(5) (Line 1). We are told that the router is a 2520, and it has a total of 8 MB of RAM (Line 7). The text "6144K/2048K bytes of memory" means that 6 MB of the RAM has been allocated for system RAM and the other 2 MB of RAM has been allocated for shared RAM. The 2520 has one Ethernet interface (Line 14), two serial (fast serial) interfaces (Line 15), two low-speed serial interfaces (Line 16), and one ISDN Basic Rate Interface (BRI) (Line 17). This 2520 has 32 kiloBytes (kB) of NVRAM (Line 18) and 16 MB of system flash (Line 19).
At the end of the message is another one of those lines telling us that NVRAM is empty (Line 21). When IOS starts, it looks in NVRAM for a configuration to load. The router's configuration contains things such as the router's name, its passwords, the protocols it is running, the interfaces it is using, and the addresses of the interfaces. This type of information should sound familiar; it is what we put in the implementation plan for the routers we are going to install (Section 3.1).
Our routers are new; therefore, there is no configuration for IOS to load. It is now our job to tell IOS what its configuration is. We will use the IOS Setup Facility.
The configuration in NVRAM is called the startup configuration. When there is no startup configuration for IOS to load at router boot time, the IOS automatically leads us to using the Setup Facility. IOS refers to the Setup Facility as the System Configuration Dialog. During the System Configuration Dialog, IOS will ask us a few questions that allow us to create a basic configuration on the router. All we have to do, at each question, is type the answer and press <Enter>.
The System Configuration Dialog can be divided into four major sections:
Using the information we put together in Section 3.1, we are going to go through the System Configuration Dialog for both Dallas and FortWorth. The configuration created on each router with the Setup Facility will make our routers operational.
We will start by configuring Router #1 on our initial infrastructure diagram, Figure 3-2. We named that router Dallas in Figure 3-3.
The System Configuration Dialog always starts by explaining some things about how to use it and then a very important question as shown in Figure 3-8.
<<<Figure 3-8 Setup Mode Question on Dallas>>>
If you are unsure of the meaning of a question during the Initial Configuration Dialog, online help is available (Line 3). Just type ? at the question.
If you start the System Configuration Dialog and then decide that you do not want to finish, you can type <Ctrl-C> to stop the dialog (Figure 3-8, Line 4). If you abort the System Configuration Dialog on a new router, the router will shut down all of its interfaces and wait for you to do something else, like restart the System Configuration Dialog.
If you happen to make a mistake by answering a question with something other than what you want, there is no way to move backward in the dialog. You have two options:
The System Configuration Dialog provides a default answer for most questions that it asks. The default answer is shown in square brackets (Figure 3-8, Line 5). If you see a value in square brackets at the end of a question, you can either press <Enter> to accept the value if you want it, or you can type another value and press <Enter>. All answers require the <Enter> key to be pressed after them before they are accepted.
The answer to any question that requires a "Yes" or "No" answer can be abbreviated with just the letter "Y" for "Yes" or the letter "N" for "No". The answer can in uppercase or lowercase.
The System Configuration Dialog always asks first if we want to continue. In our case, we do want to continue (Figure 3-8, Line 6). The next question and output is shown in Figure 3-9.
<<<Figure 3-9 Interface Summary Question on Dallas>>>
The current interface summary allows the router to tell us about all of its interfaces and their full names. Normally we want to see the current interface summary, especially if this is our first time to configure this router.
We want to make sure that the interfaces are numbered as we expected, and, more importantly, we want to make sure that the router knows about all of its interfaces. On a fixed-configuration router, like the 2520, this isn't usually an issue; however, on a modular-configuration router, like one from the 7500-series, the router may not see all of the interfaces that we think have been installed. A modular-configuration router has all of its interfaces on cards that can be added or removed to create a custom interface configuration. Cisco calls these cards Network Interface Modules or Interface Processors, depending on the type of router in which they are to be installed.
If, when we install an interface card, we somehow do not do it just right, the router may not recognize that the new card has been installed. Examining the current interface summary is a good way of verifying the presence of the interfaces.
A global parameter is one that affects the overall operation of a router. They are not specific to an individual interface or individual network protocol. Some examples are the routers' name, its passwords, and its protocols.
As shown in Figure 3-10, the first question asked of us is essentially, "What's my name?"
<<<Figure 3-10 Setup Mode Host Name on Dallas>>>
The default name for a new router is Router; this should be changed to something that is a little more descriptive. As planned, we will call the first router Dallas (Line 3).
Some guidelines for a router's host name are given in Section 1.1.1. The host name is case sensitive; therefore, the way the name is entered at this question, is the way it will appear on the router. In Chapter 4, we will see that the name appears in the prompt of the IOS command line interface; this allows us to immediately identify which router we are configuring, just in case we forget.
If we have more than one router, the name should be changed to prevent confusion in identifying each of the routers. As an example, most people who have more than one child give each child a different name for that very reason. Of course, if you really do have more than one child, you know that sometimes you call them by the wrong name anyway.
Next, we get asked for some passwords. Using the passwords selected during our planning, we can answer these questions as shown in Figure 3-11.
<<<Figure 3-11 Setup Mode Passwords on Dallas>>>
We must answer each of these questions since they have no default answers on a new router.
The enable secret password is encrypted in the IOS configuration file to help prevent accidental exposure (Line 4). The enable password is shown in clear text (just the way you type it) in the configuration file (Line 9). Both the enable secret password and the enable password have the same purpose: they allow the person configuring the router into IOS privileged mode, which will be covered in Chapter 4. The enable secret password overrides the enable password. We must enter both because older versions of IOS software do not support the enable secret password, and if this configuration were ever to be loaded on a router running the older version of IOS, we could want to have an enable password.
The virtual terminal (VTY) password is the one used to login to the router when we have established a telnet session to the router (Figure 3-11, Line 10).
Now, the System Configuration Dialog will ask which network protocols we are going to run on this router, Dallas. We simply have to answer yes or no. Our plan states that the only routed protocols we want to run are IP, IPX, and AppleTalk. This part of the dialog is shown in Figure 3-12.
<<<Figure 3-12 Setup Mode Protocols on Dallas>>>
SNMP stands for Simple Network Management Protocol, and it is not really a network protocol. SNMP is an IP application that is used to remotely manage network devices. We are not going to run SNMP (Line 1).
LAT stands for Local Area Transport, and it is a protocol that cannot be routed. LAT must be bridged because it has no layer-3 addressing. LAT is used in terminal servers and print servers in a Digital Equipment Corporation (DEC) environment. We are not going to run LAT (Line 2).
AppleTalk is used on networks with Macintosh hosts. We are going to run it in our example internetwork; therefore, we answered yes to the question (Line 3). In an AppleTalk internetwork, networks can be part of more than one zone; each of our networks is in only one. The RTMP routing protocol will automatically be used on the interfaces with AppleTalk enabled.
DECnet is used in DEC internetworks. DEC internetworks typically have host systems from DEC VAX family. We are not going to run DECnet, yet (Line 5).
Our internetwork is going to run IP; therefore, we answered yes to the question (Line 6). IOS has no default routing protocol for IP; we must select one. The System Configuration Dialog asks only about Cisco's Interior Gateway Routing Protocol (IGRP) and RIP. Our plan stated that we are to run RIP. If we wanted to run any other IP routing protocol other than IGRP or RIP, we could not use the System Configuration Dialog to start it.
CLNS stands for Connectionless Network Service, and it is a layer-3 service for the layer-3 OSI protocol Connectionless Network Protocol (CLNP). We are not going to run any OSI protocols (Line 9).
IPX is a Novell protocol that is used most of the time when a network has servers running Novell NetWare or IntraNetWare. We are going to run it in our example internetwork; therefore, we answered yes to the question (Line 10). The IPX RIP routing protocol will automatically be used on the interfaces with IPX enabled.
VINES stands for Virtual Integrated Network Services, and it is a protocol from Banyan. We are not going to run VINES, yet (Line 11).
XNS stands for Xerox Network Systems, and it is a protocol from Xerox. We are not going to run XNS (Line 12).
The question about Apollo refers to the Apollo Domain protocol which is used in Apollo workstation environments. We are not going to run the Apollo Domain protocol (Line 13).
Since messages from the protocols that we want to start in the initial configuration can be routed by their layer-3 addresses, there is no reason to start bridging during our initial configuration (Line 14).
The Cisco 2520 has an ISDN BRI interface. If we were to use it, we would have to tell IOS what type of ISDN switch to which the BRI is connected. The ISDN switch type is provided by the ISDN service provider. We are not going to use the BRI during the initial configuration (Figure 3-12, Line 15).
Now we can start telling IOS which interfaces in the router that we want to use. For each interface, the System Configuration Dialog will ask the question, "Is this interface in use?" Our routers are new; therefore, none our interfaces are in use, yet. We can interpret this question as "Do you want to use this interface now?" Our plan states that we want to use Ethernet0 and Serial1 on Dallas.
For each of the interfaces we want to initially configure, we are asked for basic information about the protocols we said we were going to run in the Global Parameters section. Figure 3-5 shows the information we need to configure the interfaces. The dialog for configuring the interfaces is shown in Figure 3-13.
<<<Figure 3-13 Setup Mode Interface Parameters on Dallas>>>
Our initial internetwork configuration does not require the use of interface BRI0 (Line 4).
Interface Ethernet0 will be used in our internetwork (Line 7). We planned to run IP, IPX, and AppleTalk on Ethernet0; therefore, we get asked about them.
The IP address 172.16.10.1 (Line 9) is from Figure 3-5. The question about the number of bits in the subnet field is rather strange (Line 10). All IP addresses have an associated network mask; we documented the network masks in Figure 3-4. The network mask we defined for this Ethernet is 255.255.255.0. The System Configuration Dialog assumes that an IP address has three fields - network, subnet, and host, and it asks us for only subnet; it can determine the rest on its own.
The combination of the IP address class and network mask defines how many bits of an IP address are in the network and subnet fields. Our planned address is a class B address; therefore, it automatically has 16 bits in its network field. The default network mask for a class B address is 255.255.0.0. We have extended the number of binary ones in that mask by eight bits to get a network mask of 255.255.255.0; therefore, we have eight bits in the subnet field. The mask is shown as /24; this is a relatively new way of displaying the mask. All this means is that 24 bits in the network mask are binary ones, or 24 bits of the IP address are used to define the network address; the other eight bits (out of 32) define an individual node on the network. IP addressing is explained in Chapter 7.
There are two versions of AppleTalk - Phase 1 and Phase 2. Normally, newer networks run Phase 2, which uses extended addressing. Extended addressing uses a cable range to address a network. From Figure 3-5, our AppleTalk cable range for Ethernet0 is 100-109. This makes 100 the starting address in the cable range (Line 14) and 109 the ending address in the cable range (Line 15). Ethernet0 is in the Headquarters zone (Line 16). AppleTalk addressing is explained in Chapter 9.
For IPX, all we need for now is a network number. From Figure 3-5, the network number for Ethernet0 is AC100A00 (Line 18). IPX addressing is explained in Chapter 8.
Interface Serial0 will not be used in our internetwork's initial implementation (Line 21).
Interface Serial1 will be used in our internetwork (Line 24); therefore, we assigned our predetermined IP, IPX, and AppleTalk addressing to it. This information again came from our plan documentation in Figure 3-4 and Figure 3-5.
There is one extra question on a serial interface's IP setup. The System Configuration Dialog asks if we want to run IP unnumbered on this interface (Line 26). This question is asked on each serial interface after another interface has been given an IP address. We gave Ethernet0 an IP address; therefore, we got the question. IP unnumbered is a mechanism used to route IP traffic on an interface without actually assigning the interface its own IP address. We have assigned an IP address to Serial1; therefore, we will not use IP unnumbered.
Interface Serial2 will not be used in our internetwork (Line 39) and neither will the Serial3 interface (Line 42).
The conclusion of the System Configuration Dialog consists of a display of the command script created from our answers to the questions and then the last, very important question. All of this is shown in Figure 3-14.
<<<Figure 3-14 Setup Mode Conclusion on Dallas>>>
The script shows some of the commands we would have to type if were not using the System Configuration Dialog to assist us. These are the commands that will be executed by IOS if we accept them.
The last thing the System Configuration Dialog wants to know is if we want to use this configuration or if we want to execute the commands (Line 57). If we answer no to this question, the new router would shut down all of its interfaces and wait for us to do something else.
We accepted the configuration by typing yes. The System Configuration Dialog then did a couple of things on the router. It executed the commands so they became part of the running configuration, and it saved them to the startup configuration in NVRAM so they would execute the next time the router boots. The messages we get after a yes answer are shown next.
The IOS commands in NVRAM are stored in a format that makes them quick and easy to display. Converting them to this format takes a few seconds. The message "Building configuration:" indicates that IOS is doing the conversion (Line 58). The "[OK]" indicates completion.
Any configuration changes that need to be done after running the System Configuration Dialog should normally be done manually using configuration mode commands.
Immediately after the completion of the System Configuration Dialog, IOS sends messages to the console about the status of the router's interfaces. After these have stopped, you can press <Enter> for a command line prompt.
Router #2 on our initial infrastructure diagram, Figure 3-2, was named FortWorth in Figure 3-3. We will run the System Configuration Dialog for FortWorth, and the answers to the questions will be very similar to those we gave for Dallas. The complete dialog is shown for consistency.
The introduction for FortWorth looks exactly like the introduction for Dallas.
--- System Configuration Dialog ---
At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets ''.
Would you like to enter the initial configuration dialog? [yes]: yes
First, would you like to see the current interface summary? [yes]: yes
Any interface listed with OK? value "NO" does not have a valid configuration
Interface IP-Address OK? Method Status Protocol
BRI0 unassigned NO unset up down
BRI0:1 unassigned YES unset down down
BRI0:2 unassigned YES unset down down
Ethernet0 unassigned NO unset up up
Serial0 unassigned NO unset up down
Serial1 unassigned NO unset down down
Serial2 unassigned NO unset up down
Serial3 unassigned NO unset down down
We want to run the initial configuration dialog and we at the interface summary to make sure that all of FortWorth's interfaces are seen by IOS. FortWorth has the same types of interfaces as Dallas.
We will set the name of the router to FortWorth. We will use the same passwords as we did on Dallas so that we do not have to remember so many. FortWorth is also running IP, IPX, and AppleTalk.
Configuring global parameters:
Enter host name [Router]: FortWorth
The enable secret is a one-way cryptographic secret used
instead of the enable password when it exists.
Enter enable secret: itsasecret
The enable password is used when there is no enable secret
and when using older software and some boot images.
Enter enable password: enableme
Enter virtual terminal password: letmein
Configure SNMP Network Management? [yes]: no
Configure LAT? [yes]: no
Configure AppleTalk? [no]: yes
Multizone networks? [no]: no
Configure DECnet? [no]: no
Configure IP? [yes]: yes
Configure IGRP routing? [yes]: no
Configure RIP routing? [no]: yes
Configure CLNS? [no]: no
Configure IPX? [no]: yes
Configure Vines? [no]: no
Configure XNS? [no]: no
Configure Apollo? [no]: no
Configure bridging? [no]: no
Enter ISDN BRI Switch Type [none]: none
Now it is time to tell IOS which interfaces we will be using for the initial internetwork.
According to our plan documentation in Figure 3-5, FortWorth will be using interfaces Ethernet0 and Serial0. Each of these interfaces gets IP, IPX, and AppleTalk information assigned to it.
Configuring interface parameters:
Configuring interface BRI0:
Is this interface in use? [yes]: no
Configuring interface Ethernet0:
Is this interface in use? [yes]: yes
Configure IP on this interface? [yes]: yes
IP address for this interface: 172.16.20.1
Number of bits in subnet field : 8
Class B network is 172.16.0.0, 8 subnet bits; mask is /24
Configure AppleTalk on this interface? [no]: yes
Extended AppleTalk network? [no]: yes
AppleTalk starting cable range : 200
AppleTalk ending cable range : 209
AppleTalk zone name [myzone]: Twilight
Configure IPX on this interface? [no]: yes
IPX network number : ac101400
Configuring interface Serial0:
Is this interface in use? [yes]: yes
Configure IP on this interface? [yes]: yes
Configure IP unnumbered on this interface? [no]: no
IP address for this interface: 172.16.11.2
Number of bits in subnet field : 8
Class B network is 172.16.0.0, 8 subnet bits; mask is /24
Configure AppleTalk on this interface? [no]: yes
Extended AppleTalk network? [yes]: yes
AppleTalk starting cable range : 1001
AppleTalk ending cable range : 1001
AppleTalk zone name [myzone]: WAN
Configure IPX on this interface? [no]: yes
IPX network number : ac100b00
Configuring interface Serial1:
Is this interface in use? [yes]: no
Configuring interface Serial2:
Is this interface in use? [yes]: no
Configuring interface Serial3:
Is this interface in use? [yes]: no
This is almost too easy. We might as well finish it.
Examine the command script and answer the final question.
The following configuration command script was created:
enable secret 5 $1$LKJD$eQwhzhNEr4LsUFCwrJ8eG0
enable password enableme
line vty 0 4
no decnet routing
no clns routing
no vines routing
no xns routing
no apollo routing
no bridge 1
isdn switch-type none
no ip address
ip address 172.16.20.1 255.255.255.0
appletalk cable-range 200-209
appletalk zone Twilight
ipx network AC101400
ip address 172.16.11.2 255.255.255.0
appletalk cable-range 1001-1001
appletalk zone WAN
ipx network AC100B00
no ip address
no ip address
no ip address
Use this configuration? [yes/no]: yes
Use the enabled mode 'configure' command to modify this configuration.
Press RETURN to get started!
Now that FortWorth's initial configuration is complete, we can connect the interfaces.
Before you turn on a router for the first time, you should have some idea of what you are going to do with it because it is going to ask you to go through an initial configuration dialog and build a skeletal configuration on the router. I call the configuration a skeletal configuration because of its bare bones nature. The System Configuration Dialog allows you to turn on interfaces, assign addresses, and assign some passwords; however, it does not allow you to customize IOS configuration things like routing protocols and filters. With the System Configuration Dialog, we can quickly put a configuration on a router to allow the interfaces to come up and IOS to start routing and/or bridging. From there, we can make modifications. Just remember that a little up-front design work never hurt anybody. Our planning allowed us to very quickly run through the initial configurations two routers, Dallas and FortWorth.
The process you have just seen is generally what it will look like. Of course, your mileage may vary based on the router model, the IOS version, and the protocols you need.
A router's interface must be connected to a network so messages may be received and routed or bridged from one network to another. This connection is as simple as plugging one end of an appropriate cable into the router's interface and then plugging the other end of the cable into the physical network equipment such as an Ethernet hub or a T1 CSU/DSU (Channel Service Unit/Digital Service Unit). In our internetwork, we are using Ethernet and serial interfaces. These should be connected to their respective networks.
Our routers are now configured and operational. The routers' interfaces are connected to their networks, and the networks are operational. We now have a working internetwork.