Slide 1Cisco IOS File System and Devices
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16384K bytes of processor board System flash (Read ONLY)
Emphasize: The show flash command is an important tool to use to gather information about your router memory and image file. Caution students that they must know that they are loading the correct and appropriate image. The name for the Cisco IOS image file contains multiple parts, each with a specific meaning:
The first part of the image name contains the platform on which the image runs. In this example, the platform is C2500.
The second part of the name identifies the special capabilities of the image file. A letter or series of letters identifies the feature sets supported in that image. In this example, the “j” indicates this is an enterprise image, and the “s” indicates it contains extended capabilities.
The third part of the name specifies where the image runs and if the file is compressed. In this example, “l” indicates the file is relocatable and not compressed. Relocatable means the Cisco IOS can be run from Flash or from RAM. You should be careful in reading the Cisco IOS image filename. Some fonts display the lowercase letter “l” and the number 1 as the same character. How you enter the characters will impact the ability of the router to load the files correctly.
The fourth part of the name indicates the version number. In this example, the version number is 12.0 (3).
The final part of the name is the file extension. The .bin extension indicates this file is a binary executable file.
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Creating a Software Image Backup
Purpose: This slide discusses how to create a backup version of a Cisco IOS software image to a TFTP server.
Emphasize: Routers by default come with Flash memory that has a preloaded copy of the Cisco IOS software. Although Flash is extremely reliable—good for 65 years and 100,000 rewrites—it is a good idea to make a backup copy of the Cisco IOS software if you have a TFTP server available. If you have to replace Flash memory for some reason, you will have a backup copy at the revision level currently running on your network.
The copy command screen output varies depending on the Cisco IOS software level.
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Upgrading the Image from the Network
Purpose: This slide describes how to load a backup version of a Cisco IOS software image from a TFTP server to the router.
Emphasize: If you need more Flash space to load a copy of the Cisco IOS software, you must first erase the Flash memory. You cannot erase a single image—you must erase all copies of Cisco IOS software from Flash. However, if Flash memory on the router is partitioned, you can erase one or more of the parts.
After the TFTP transfer is completed, use the show flash command to view the file size to compare its size with that of the original on the server.
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Connect the machine to a Router
To see the content of Flash file
#show Flash
To copy running-configuration
#copy running-config tftp
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Resolving Host Names
To use a hostname rather than an IP address to connect to a remote device
Two ways to resolve hostnames to IP addresses
building a host table on each router
building a Domain Name System (DNS) server
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To view table
R1#show hosts
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This means that bits 13, 8, and 1 are on.
To ignore NVRAM the 6th bit should be made ON
When the 6th bit is turned on the value will be 2142
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Password is stored in NVRAM
To by pass NVRAM during boot sequence we need to change the configuration register value
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WAN speed is less
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Remote Access Overview
A WAN is a data communications network covering a relatively broad geographical area.
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Service
Provider
Purpose: This figure introduces students to WAN connections.
Emphasize: Highlight the interconnected WAN connections between the various company sites. The site graphically present a mobile dial-up user, a telecommuter using a DDR connection, and two office sites with multiple connections.
This course teaches students how to configure a WAN. Tell students a WAN is a data communications network that serves users across a broad geographic area.
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WAN technology/terminology
Devices on the subscriber premises are called customer premises equipment (CPE).
The subscriber owns the CPE or leases the CPE from the service provider.
A copper or fiber cable connects the CPE to the service provider’s nearest exchange or central office (CO). A central office (CO) is sometimes referred to as a point of presence (POP)
This cabling is often called the local loop, or "last-mile".
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WAN technology/terminology
A demarcation point is where customer premises equipment (CPE) ends, and local loop begins.
The local loop is the cabling from demarcation point to Central Office (CO).
A dialed call is connected locally to other local loops, or non-locally through a trunk to a primary center.
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WAN technology/terminology
Devices that put data on the local loop are called data communications equipment (DCE).
The customer devices that pass the data to the DCE are called data terminal equipment (DTE).
The DCE primarily provides an interface for the DTE into the communication link on the WAN cloud.
The DTE/DCE interface uses various physical layer protocols, such as V.35.
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Modems transmit data over voice-grade telephone lines by modulating and demodulating the signal.
The digital signals are superimposed on an analog voice signal that is modulated for transmission.
The modulated signal can be heard as a series of whistles by turning on the internal modem speaker.
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WANs - Data Link Encapsulation
The data link layer protocols define how data is encapsulated for transmission to remote sites, and the mechanisms for transferring the resulting frames.
A variety of different technologies are used, such as ISDN, Frame Relay or Asynchronous Transfer Mode (ATM).
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Use transmission facilities leased from service provider
Carries different traffic (voice, video and data)
Dedicated
T series in U.S. and E series in Europe
Uses time division multiplexing and assign time slots for transmissions
T1 = 1.544 Mbps E1 = 2.048 Mbps
T3 = 44.736 Mbps E3 = 34.368 Mbps
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Digital Subscriber Line (DSL) technology is a broadband technology that uses existing twisted-pair telephone lines to transport high-bandwidth data to service subscribers.
The two basic types of DSL technologies are asymmetric (ADSL) and symmetric (SDSL).
All forms of DSL service are categorized as ADSL or SDSL and there are several varieties of each type.
Asymmetric service provides higher download or downstream bandwidth to the user than upload bandwidth.
Symmetric service provides the same capacity in both directions.
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Dial-up Modems (switched analog)
Standard that can provides 56 kbps download speed and 33.6 kbps upload speed.
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Cable Modems (Shared Analog)
Cable TV provides residential premises with a coaxial cable that has a bandwidth of 750MHz
The bandwidth is divided into 6 MHz band using FDM for each TV channel
A "Cable Modem" is a device that allows high-speed data access (Internet) via cable TV network.
A cable modem will typically have two connections because a splitter delivers the TV bands to TV set and the internet access bands to PC via a cable box
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Cost is relatively low
Line-of-sight is usually required
Usage is widespread
Max. bandwidth = 128 kbps for BRI (Basic Rate Interface)
2 B channels @ 64kps and 1 D channel @ 16kps
B channels are voice/data channels; D for signaling
B
B
D
Asynchronous Transfer Mode (ATM)
Communications providers saw a need for a permanent shared network technology that offered very low latency and jitter at much higher bandwidths.
ATM has data rates beyond 155 Mbps.
ATM is a technology that is capable of transferring voice, video, and data through private and public networks.
It is built on a cell-based architecture rather than on a frame-based architecture.
ATM cells are always a fixed length of 53 bytes.
The 53 byte ATM cell contains a 5 byte ATM header followed by 48 bytes of ATM payload.
Small, fixed-length cells are well suited for carrying voice and video traffic because this traffic is intolerant of delay.
Video and voice traffic do not have to wait for a larger data packet to be transmitted.
The 53 byte ATM cell is less efficient than the bigger frames and packets of Frame Relay
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Leased lines
It is a pre-established WAN communications path from the CPE, through the DCE switch, to the CPE of the remote site, allowing DTE networks to communicate at any time with no setup procedures before transmitting data.
Circuit switching
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Packet switching
WAN switching method that allows you to share bandwidth with other companies to save money. As long as you are not constantly transmitting data and are instead using bursty data transfers, packet switching can save you a lot of money.
However, if you have constant data transfers, then you will need to get a leased line.
Frame Relay and X.25 are packet switching technologies.
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Defining WAN Encapsulation Protocols
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Point-to-Point Protocol (PPP)
High-Level Data Link Control Protocol (HDLC)
X.25 / Link Access Procedure Balanced (LAPB)
Frame Relay
Availability
Each type of service may be available in certain geographical areas.
Bandwidth
Determining usage over the WAN is important to evaluate the most cost-effective WAN service.
Cost
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WAN Type
Maximum Speed
Asynchronous Dial-Up
56-64 Kbps
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Leased Line
Telephone
Company
Service
Provider
Purpose: This figure introduces students to various encapsulation options to use over the various physical connections.
Emphasize: In order to exchange traffic over a WAN link, the packets must be encapsulated into a Layer 2 frame. There are a variety of Layer 2 encapsulation types available that can be used, depending on the WAN connection being used. Some of the types are listed on the figure.
Encapsulation must be configured on the router when configuring the interface. Some of these encapsulation types will be seen again in the following chapters.
In an ISDN environment, Point-to-Point (PPP) is the B channel’s Layer 2 encapsulation. Link Access Procedure on the D channel (LAPD) is the encapsulation for the D channel.
Either the proprietary Cisco or Internet Engineering Task Force (IETF) (defined in RFC 1490) encapsulations are the Layer 2 encapsulations for Frame Relay.
Note: Other encapsulations not shown include AppleTalk Remote Access Protocol (ARAP), Compressed Serial Link Internet Protocol (CSLIP), or Synchronous Data Link control (SDLC).
Transition: We will first look at the HDLC encapsulation.
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Multipoint - Frame Relay, X.25 and ATM
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WAN
LAN
Network
Datalink
Physical
PPP - Open
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Address
Control
Proprietary
Data
FCS
Flag
Cisco’s HDLC has a proprietary data field to support
multiprotocol environments
Purpose: This figure introduces students to HDLC encapsulation.
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synchronous serial interfaces
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PPP is made up of LCP and NCP
LCP is for link control and NCP for multiple protocol support and call back
PPP Encapsulation
Emphasize: The figure illustrates the multiple protocols NCP supports.
The two arrows pointing to the router interfaces is where PPP encapsulation occurs.
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Multilink
Protocol (MP)
Purpose: The figure presents an overview of the most popular PPP features.
Emphasize: The table in the figure lists and describes the various LCP options.
PPP compression is offered in Cisco’s Compression Control Protocol (CCP).
RFC 1548 covers the Internet Engineering Task Force (IETF) approved PPP options in detail. RFC 1717 defines Multilink Protocol. RFC 1990, The PPP Multilink Protocol (MP), obsoletes RFC 1717.
Note: To further enhance security, Cisco IOS Release 11.1 offers callback over PPP. With this LCP option, a Cisco router can act as a callback client or as a callback server.
The client makes the initial DDR call requests that it be called back, and terminates its initial call. The callback server answers the initial call and makes the return call to the client based on its configuration statements.
This option is described in RFC 1570.
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Purpose: This graphic presents the PPP authentication overview.
Emphasize: A PPP session establishment has three phases:
Link establishment phase—In this phase, each PPP device sends LCP packets to configure and test the data link.
Authentication phase (optional)—After the link has been established and the authentication protocol decided on, the peer may be authenticated.
PPP supports two authentication protocols: PAP and CHAP.
Both of these protocols are detailed in RFC 1334, PPP Authentication Protocols. However, RFC 1994, PPP Challenge Handshake Authentication Protocol, obsoletes RFC 1334.
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Remote Router
Emphasize: PPP sets line controls for the call.
There are two types of authentication protocols: PAP and CHAP.
PAP provides a simple method for a remote node to establish its identity using a two-way handshake.
PAP is done only upon initial link establishment.
PAP is not a strong authentication protocol. It provides no encryption. It may be fine in DDR environments when the password changes each time one authenticates.
CHAP is the preferred protocol.
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Use “secret” known only to authenticator and peer
Remote Router
Purpose: This figure presents the PPP authentication protocol, CHAP.
Emphasize: CHAP is done upon initial link establishment and can be repeated any time after the link has been established.
CHAP transactions occur only when a link is established. The local access server does not request a password during the rest of the session. (The local access server can, however, respond to such requests from other devices during a session.)
CHAP is specified in RFC 1334. It is an additional authentication phase of the PPP Link Control Protocol.
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Service
Provider
ppp encapsulation
ppp encapsulation
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Purpose: This figure provides a sign post highlighting the tasks to complete to enable PPP and PPP authentication.
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Router(config-if)#encapsulation ppp
Enable PPP encapsulation
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Router(config)#username name password password
Identifies the username and password of authenticating router
Purpose: This figure describes how to set the hostname on the local device and a remote device’s username and password.
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Enables PAP and/or CHAP authentication
Purpose: This figure continues with the PPP authentication configuration commands.
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R1
R2
PSTN/ISDN
Purpose: This page shows an example of CHAP configuration between two routers.
Emphasize: When you configure the usernames and passwords for the local databases, the passwords on both systems must be identical. Usernames and passwords are case sensitive.
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Router#show interface s0
Hardware is HD64570
Internet address is 10.140.1.2/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation PPP, loopback not set, keepalive set (10 sec)
LCP Open
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
38021 packets input, 5656110 bytes, 0 no buffer
Received 23488 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
38097 packets output, 2135697 bytes, 0 underruns
0 output errors, 0 collisions, 6045 interface resets
0 output buffer failures, 0 output buffers swapped out
482 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up
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4d20h: %LINK-3-UPDOWN: Interface Serial0, changed state to up
4d20h: Se0 PPP: Treating connection as a dedicated line
4d20h: Se0 PPP: Phase is AUTHENTICATING, by both
4d20h: Se0 CHAP: O CHALLENGE id 2 len 28 from ”left"
4d20h: Se0 CHAP: I CHALLENGE id 3 len 28 from ”right"
4d20h: Se0 CHAP: O RESPONSE id 3 len 28 from ”left"
4d20h: Se0 CHAP: I RESPONSE id 2 len 28 from ”right"
4d20h: Se0 CHAP: O SUCCESS id 2 len 4
4d20h: Se0 CHAP: I SUCCESS id 3 len 4
4d20h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
debug ppp authentication successful CHAP output
R1
R2
Service
Provider
debug ppp authentication
Purpose: This page shows an example of debug ppp authentication output. The output illustrates of a successful CHAP authentication challenge.
Emphasize: The debug ppp authentication command displays the authentication exchange sequence as it occurs.
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Purpose: this figure describes various ISDN environments.
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Telephone services -> Telecommunication services
used for studo quality sound and moving images
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Channel
Purpose: The figure explains BRI and PRI.
Emphasize: Be aware of geographic variations regarding ISDN services. With PRI, for example, there are 23 B channels in the United States and Japan and 30 in Europe.
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Multiple devices
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S/T interface
U interface
ISDN Switch
Interfaces and Devices
Function Group – A set of functions implemented by a device or software
Reference Point – The interface between two function group
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R1(config-if)#int bri 0
R1(config-if)#enacapsulation ppp
R1(config)#ip route 0.0.0.0 0.0.0.0 10.0.0.2
R1(config)#isdn switch-type basic-net3
R1(config)#int bri 0
R1(config-if)# dialer–group 1
R1(config-if)#no shut
2) ISDN Switch
3) R1, BRI should be connected to 20 line of ISDN switch
4) ISDN status can give the call establishing
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username name name password secret
Global command that configure CHAP username and password
access-list
Global command that creates ACL’s to define a subset of traffic as interesting
dialer-list 1 protocol IP
Global command that creates a dialer list that makes all IP traffic interesting or reference to ACL for subset
dialer–group 1
Interface subcommand that references dialer list to define what is interesting
dialer idle-timeout 100
dialer string number
int bri 0
Global command that selects BRI interface
dialer map command is used to associate an ISDN phone number
with the next hop router address.
ping and telnet Great IP tools for any network. However, your interesting traffic restriction
must dictate that Ping and Telnet are acceptable as interesting traffic
in order to bring up a link. Once a link is up, you can ping or telnet to
your remote router regardless of your interesting traffic lists.
show dialer Gives good diagnostic information about your dialer and shows the
number of times the dialer string has been reached, the idle-timeout values
of each B channel, the length of the call, and the name of the router
to which the interface is connected.
show isdn active Shows the number called and whether a call is in progress.
show isdn status
Reliable--X.25 has been extensively debugged and is now very stable--literally no errors in modern X.25 networks
Store & Forward--Since X.25 stores the whole frame to error check it before forwarding it on to the destination, it has an inherent delay (unlike Frame Relay) and requires large, expensive memory buffering capabilities.
Frame Relay (Connectionless)
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FR developed in 1984, its a faster packet switching technology
In 1990 FR consortium was developed and extension added
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Access Line
Trunk Line
Virtual Circuit – an end to end connection between interface device - PVC or SVC
Data Link connection Identifiers (DLCI) number is the identification for VC, 16-1007
Committed Information Rate or CIR - agreed-upon bandwidth
Frame Relay there are two encapsulation types: Cisco and IETF
Local Management Interface (LMI) is a signaling standard used between your router and the first Frame Relay switch i - Cisco, ANSI, and Q.933A.
frame-relay lmi-type
Frame Relay differs from X.25 in several aspects.
Much simpler protocol that works at the data link layer, not the network layer.
Frame Relay implements no error or flow control.
The simplified handling of frames leads to reduced latency, and measures taken to avoid frame build-up at intermediate switches help reduce jitter.
Most Frame Relay connections are PVCs rather than SVCs.
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FRSwitch(config-if)#no shut
R1(config-if)#enacapsulation frame-relay
R1(config-if)#no shut