Cisco Internetworking Operating System
Cisco IOS software is developed and maintained by Cisco to support a full array of system functions, applications (including Internet applications), and network hardware in a single software package. IOS software is installed on each Cisco router or switch and can accommodate network growth and provide for secure data transfers. The command-line interface (CLI) for routers and switches defines the commands that are used to communicate with the IOS. Future chapters demonstrate the use of CLI commands on both network devices.
Cisco releases IOS software using what they call trains. Each release can be further defined by train identifiers. A train identifier determines whether a release is a Technology (T), Enterprise, or Service Provider (SP) release. When the IOS version has no train identifier, it is the mainline train. With so many features and applications being offered with each release, a train identifier can further define a specific subset of features. For example, if you have a release named 12.3(1)T, the IOS version number breaks down as follows:
- 12.3 refers to the mainline train that will not be added to but will be subject to IOS bug fixes.
- (1) represents the release number, which increments with each new release of the mainline train.
- T identifies the type of train release where T stands for Technology. This may also be an S (Service Provider) or E (Enterprise) train.
A feature set is a package of the features that is offered in addition to the basic IOS functions of an IOS software release. You can select more than one feature set per release. Feature sets may be identified as standard, enhanced, or advanced, depending on the services that are supported. To give you an idea of the latest features available with Cisco IOS, current releases
offer the following software functionality:
- IP Base—The base IOS image.
- IP Voice—Features include Voice over IP (VoIP), and Voice over Frame (VoFR).
- Advanced Security—Offers advanced protection via firewall, Intrusion Detection
System (IDS), Secure Shell (SSH), and IP Security (IPSec).
- SP Services—Includes service provider services such as IPv6, Netflow SSH, ATM, Voice over ATM (VoATM), and Frame Relay.
- Enterprise Base—Consists of Enterprise Layer 3 routed protocols, and IBM support.
- Advanced IP Services—Offers a combination of the Advanced Security and Service Provider Services feature sets.
- Enterprise Services—Combines the Enterprise Base and Service Provider Services feature sets with full IBM support.
- Advanced Enterprise Services—Incorporates all the Cisco IOS feature sets.
IOS Image File Naming
The IOS image file represents the name of the system image on a Cisco router or switch. The hardware platform, feature set, compression format, IOS version, and train information are all found in the name of an IOS image file. An IOS image filename can be broken out to identify more specific information about the IOS in use by a device. This is helpful if you are troubleshooting a system issue and need to verify what version is currently in use. Cisco may be aware of an IOS bug, or the version may simply be outdated and an IOS upgrade might be the solution to your trouble. To find the IOS image filename, use the show version command from the command prompt. Given the example filename c2600-ipbase-1.122-1.T.bin (.bin indicates binary format), from left to right, each portion of the filename represents the following:
- c2600—Hardware platform (Cisco 2600 router)
- ipbase—Feature set
- 1 —File format (compressed re-locatable)
- 122—IOS version number
- 1 —Maintenance release number
- T—Train identifier
Remember the IOS image file structure. If given a filename, you should be able to break down each
part of the file and what it represents.
Cisco Router Models and Features
. Describe the purpose and functions of various network devices
Cisco offers a wide selection of router models for network implementations. The Cisco family of routers can accommodate networks that range in size and require various network interfaces for WAN connectivity. As mentioned, some router models are fixed port and fixed configuration, whereas others are modular-port routers. To help you prepare for the CCNA exam, a Cisco 2500 series router model can perform a broad range of the basic routing functions. This router can provide you with sufficient functionality to practice initial router setup and configurations.
The 2500 series hardware can support CSU/DSU, ethernet, token ring, asynchronous or synchronous serial, and ISDN connections. The 2500 series routers coupled with Cisco IOS software can support routed protocols such as IP, Novell IPX, and AppleTalk. They can also support a wide array of routing protocols. Although most of the 2500 family routers are fixed
port, the 2524 and 2525 models are both modular-port routers. In addition to the 2500 series routers, Cisco also offers the following router series:
- 800 Series—Fixed-port and fixed-configuration routers that support Asymmetric Digital Subscriber Line (ADSL), ADSL over ISDN, Single-pair High-Speed DSL (G.SHDSL), Serial, and ethernet to an external cable modem or DSL connections. They can also support a small office or a home office for a telecommuter.
- 1600 Series—Fixed-port routers that support ISDN, asynchronous serial, or synchronous serial connections and can support a small- to moderately-sized business.
- 1700 Series—Modular-port routers that support built-in Fast Ethernet LAN ports and WAN/Voice modular slots, and can support a small- to moderately-sized business.
- 1800 Series—Fixed-port and modular-port routers that build on the 1700 Series router functionality with integrated services such as IPSec VPN, firewall security, inline intrusion prevention (IPS), Network Admission Control (NAC), and URL filtering to small offices.
- 2600 Series—Modular multiservice access routers that support built-in ethernet LAN ports, built-in Fast Ethernet LAN ports, and WAN/voice modular slots. They can support a small to medium office.
- 2800 Series—Integrated service routers that support built-in Fast Ethernet LAN ports, built-in Gigabit Ethernet LAN ports, and WAN/voice modular slots. They can support a small to medium office, its telecommuters, and Wi-Fi connections.
- 3600 Series—Modular multiservice access routers that support data, voice, video, and VPN. They can support a medium to large office or a small Internet Service Provider (ISP).
- 3700 Series—Modular multiservice access routers that support built-in Fast Ethernet LAN ports and WAN/voice modular slots. They can support branch offices.
- 3800 Series—Modular multiservice access routers that support built-in dual Gigabit Ethernet LAN ports and enhanced network module slots. They can support a medium to large business with integrated services.
- 7200 Series—Can be used with an Enterprise Edge or Service Provider Edge environment and support links that range in size from a DS0 (64Kbps) all the way up to an OC12 (655Mbps). They can support Fast Ethernet, Gigabit Ethernet, and Packet over Sonet connections. Chassis slots are open for installation of more than 70 network interfaces.
- 7600 Series—Are likely to be found in a main office of an enterprise business or at a
small service provider’s point-of-presence (POP) site. Each chassis can support a maximum of 4 slots. Each slot has either a 40Gbps or 720Gbps capacity with advanced optical service modules.
Cisco Switch Models and Features
- Describe the purpose and functions of various network devices
The Cisco family of switches includes the Catalyst switch models, which as you learned earlier in this chapter might use the Cat OS rather than the IOS. As with Cisco routers, the switch model numbers increase as they are upgraded for enhanced overall operability. Various switches have been developed over the years to accommodate the size and functionality requirements of LANs around the world. You may have a Cisco 1900, 2800, 2900, or 2924 switch to help you study for the Cisco Certified Network Associate exam. These models should be easy to find and affordable, and they cover all the features necessary for the exam when coupled with Cisco IOS. In addition to the 1900, 2800, 2900, and 2924 series switches, Cisco also offers the following switch series:
- 2950 Series—Includes a fixed-configuration switch that can support both Fast Ethernet and Gigabit Ethernet connections.
- 3500 Series—Are stackable switches that can employ Cisco Switch Clustering technology and GigaStack GBICs, and support Layer 3 functionality.
- 4000 Series—Can support high-density copper, fiber-based interfaces, Fast Ethernet, Gigabit Ethernet connections, and Layer 3 functionality.
- 6500 Series—Can support Power over Ethernet (PoE) devices, 10/100Mbps ethernet ports, 10/100/1000Mbps ethernet ports, 10Gbps ethernet ports, and Layer 3 functionality.
Cisco switches may also support PoE. PoE enables an end device to receive power over a copper ethernet cable. End devices that might use PoE include wireless access points, IP telephones, video cameras, and card scanners. This technology was originally developed by Cisco and called “inline power.” IEEE has since standardized PoE with 802.3af.