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For the courtesy of others…

Cell phones may be put on vibrate mode, but please take the call outside of the room.

LAN, WAN, Internetworks

Local Area Network (LAN) - An individual network administered by a single organization , usually spans a single geographical area.

Wide Area Network (WAN)- Individual organizations usually lease connections through a telecommunications service provider (TSP) .

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T1, DS3, OC3 PPP, HDLC Frame Relay, ATM ISDN, POTS

Today’s popular communication tools

1- Instant Messaging

A real-time communication by typing text. Developed from earlier Internet Relay Chat (IRC) services . Incorporates features such as: file transfer, voice ,video communication (web cam), chat .

Communication starts with a an application

Protocol Data Units and Encapsulation – another example

Header

Header Data

Header Trailer

Email Message

Data Data Data

Data

Data

0010100111011001010000011111010100010101

Segmentation and Encapsulation

Protocol Data Units and Encapsulation

Header

Header

Header Trailer

Email Message

Data Data Data

Data

Data

Data

Decapsulation and Reassembly

Data

0010100111011001010000011111010100010101

Putting It all Together

1 .Converted to Binary.

2 .NIC generates signals that represent these bits.

3 .Passed among LAN devices.

4 .Exit the local area (router).

Putting It all Together

6 .Passed among local devices at the destination.

7. The destination device converts the bits into human readable form.

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IP Addresses – First look

Network Address 172.16.0.0

172.16.10.100/16

172.16.10.55/16

172.16.10.3/16172.16.1.1/16

ISP

Internet

Network Address 192.168.1.0/30

192.168.1.2/30

192.168.1.1/30

C:\> ipconfig

Windows IP ConfigurationEthernet adapter Local Area Connection: Connection-specific DNS Suffix . : IP Address. . . . . . . . . . . . : 172.16.10.100 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : 172.16.1.1

Routing

Each host contain a routing table that contains at the minimum a “gateway”.

The router also needs a routing table that defines where to forward the packet next. This is called the next-hop address or default route.

Network device use the Default gateway to send the data to every device on the Internet it doesn’t know its addresses.

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Domain Name System (DNS)

• DNS and the Browser:

1. The resolver sends the DNS request to the DNS Server.2. The server then searches its records and resolves the name with

to a corresponding IP Address.

2 www.cisco.com

www.cisco.com = 198.133.219.25

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Domain Name System (DNS)

• The resolver send requests to the DNS server identified in the configuration

• From the IP configuration on the device.IP Address 192.168.25.25Subnet Mask 255.255.255.0Default Gateway 192.168.25.1DNS Server 208.67.222.222

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Name Resolution

DNS queries are two types of queries:

Recursive queries

Queries performed by Host to Local DNS Server

Iterative queries

Queries performed Local DNS server to other servers

Need the IP address

Domain Name System (DNS)

• Utility - nslookup:• Windows operating systems provide the nslookup utility.• Use to query a domain name and get the IP Address.

Components of the Network

Devices (hardware) : End devices or intermediate devices.

Media : Wired or wireless media.

Services (software) :Network applications, routing protocols, processes, algorithms

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Each host is identified by two addresses.

• IP (Internet Protocol) address and a MAC address (later).

The address of the destination host is used to specify where the message should be sent.

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Source Address Destination Address

209.67.102.55 107.16.4.21

Network Representations

Network Interface Card (NIC) or LAN adapter : Provides the physical connection to the network for the host device. The media connecting the PC to the networking device plugs directly into the NIC.

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Two Address Types

• Each device has two addresses.

• A burned in Layer 2 / MAC address:

• A logical , Layer 3 / Network “protocol” Address:

This might be assigned statically or dynamicallyusing DHCP.

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DHCP

DHCP Information can include:

• IP address.• Subnet mask.• Default gateway.• Domain name.• DNS Server.

DHCP servers can be:

• Server on LAN.• Router.• Server at ISP “Accessed

remotely on t he WAN.

• Host X sends a packet to Host Y.

IP Packets: Carrying Data End to End

Remember:Two addresses are needed to move a packet from the source to the destination.

• MAC Address• IP Address

Media

The medium provides the channel over which the messages travel from source to destination.

Metallic wires within cablesGlass or plastic

fibers

Wireless Transmission

Media

Coaxial cable and connectors

Central conductor. Insulation. Copper braid acting as return path for current and also as shield against interference

(noise). Outer jacket. Used formerly in Token LANs – died out as UTP was cheaper and gave higher speeds.

Standards and Implementation

802.2LogicalLinkControl(LLC)

802.3MediaAccessControl(MAC)

Ethernet Distance Connector

10BASE5 500m Coax

10BASE2 185m Coax

10BASE-T 100m UTP-RJ45

1000BASE-T 100m UTP-RJ45

1000BASE-SX 550m MM Fiber -SC

1000BASE-LX 5000m MM/SM Fiber-SC

Ethernet 802.3

Unshielded twisted pair (UTP) cable

Eight wires twisted together into four pairs and with an outer jacket. Jackets protects copper from physical damage. Commonly used for Ethernet LANs. The number of twists per metre is carefully controlled. (Protect from

interference)

Straight through cable

Both ends the same Connect PC to switch or hub Connect router to switch or hub Installed cabling is straight through. Connects unlike devices DCE-DTE.

Crossover cable

Wire 1 swaps with 3 Wire 2 swaps with 6 Connect similar devices to each other Connect PC to router , switches to

hubs , DTE to DTE or DCE to DCE.

Rollover cable

Cisco proprietary. Wire order completely reversed. Console connection from PC serial port to router –

to configure router. Special cable or RJ45 to D9 adaptor.

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Cabling – Show the straight-through and cross-over cables

hub hub hub hub hub hub

switch switch

router

Straight-through cable

Cross-over cable

Intermediary Devices

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routers

switch or hub

switch or hub

LAN

WAN

Processes running on the intermediary network devices perform these functions:

Regenerate and retransmit data signals. Determine all network path ways available. Network address translation. Permit or deny and manage the flow of data, based on security settings.

Routers

Used to link networks together.

Routes packets to the best path based on Layer 3 IP Destination Address.

Each routers interface is connected to a different network and has an IP address/mask as a gateway for that network users.

Each interface has an IP address/mask on it’s network.

Ethernet 0

172.16.1.1 255.255.255.0 MAC: 0cddeeffaabb

Serial 0

192.168.10.1 255.255.255.252

Ethernet 1

172.16.2.1 255.255.255.0 MAC: 0abbccddeeff

Choice of router

Expandability – Fixed or modular interfaces ? Media – serial , UTP or fibre optic ports ? how many ports of each? Operating System Features – what do you want the router to do? Will you have

enough memory to upgrade the operating system? Do you need security supported IOS , VOIP,QOS.

Packet Forwarding

Routing is done packet-by-packet based on the destination IP address.

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Routing – First Look

Routers know about routes either statically or dynamically using a routing protocol:• Directly connected networks (C):

Network addresses of its interfaces• Remote networks : learned by static or dynamic Routing Protocol (R = RIP)

192.168.1.254/24

C 192.168.2.0/24 is direction connected, FastEthernet0/1

Network 192.168.2.0/24

Network 192.168.1.0/24

Destination Network Next Hop

Metric

Destination Network - Routing Table Entries

• The default route in a routing table performs as a default gateway in a PC.

• If a route for a packet cannot be found in the routing table, and a default route is present, that route will be used to forward the packet.

• A next-hop is the address of the device that will process the packet next.

Packet Forwarding: Route Found

L2 IP TCP DATA L2

IP TCP DATA

Data for Host 10.1.2.2 / 24

Network 10.1.1.0

Network 10.1.2.0

L2 IP TCP DATA L2IP Address 10.1.2.2 is on network 10.1.2.0

Packet Forwarding: Default Route

L2 IP TCP DATA L2

IP TCP DATA

Data for Host 207.1.1.1 / 24

Network 10.1.1.0

Network 10.1.2.0

L2 IP TCP DATA L2IP Address 207.1.1.1 is on network 207.1.1.0

Packet Forwarding: Route Not Found

L2 IP TCP DATA L2

IP TCP DATA

Data for Host 207.1.1.1 / 24

Network 10.1.1.0

Network 10.1.2.0

IP Address 207.1.1.1 is on network 207.1.1.0

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Private IP Addresses

RFC 1918

• 10.0.0.0 to 10.255.255.255 (10.0.0.0 /8)• 172.16.0.0 to 172.31.255.255 (172.16.0.0 /12)• 192.168.0.0 to 192.168.255.255 (192.168.0.0 /16)

• Need NAT/PAT if it requires to access the internet (next).• These addresses should not be routed in the Internet “Should be blocked by

your ISP.

Data communications equipment and Data terminal equipment

• Data Communications Equipment (DCE) – is a device that supplies the clocking services to another device. The clocking service is needed in WAN to synchronize the transmitted signal. Typically, this device is at the WAN provider end of the link.

• Data Terminal Equipment (DTE) – is device that receives clocking services from another device . This device is at the WAN customer or user end of the link.

• A router is by default a DTE device . Nevertheless, it can be configured to be a DCE by assigning a clock rate to the router.

The purpose of Cisco IOS Software

As with a computer, a router or switch or other Cisco devices cannot function without an operating system “IOS:.

Cisco “IOS” Internetwork Operating System is stored in the flash memory but can be over written”.

The IOS is copied into RAM to run from there when the device is powered on . This function increases the performance of the device.

The IOS can be accessed using http or command line interface.

Router internal components Similar to PC

CPU Memory

• RAM • Flash • NVRAM • Rom

• Buses • Interfaces • Power Supply

Router storage areas

ROM

Permanent. Holds POST, boot instructions,

basic IOS.

Flash

Keeps contents Holds one or more IOS images

NVRAM

Keeps contents Holds startup configuration file

RAM

Volatile Holds runnning config, tables,

queues etc

Initial startup of Cisco routers

When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all

hardware modules. After the POST, the following events occur as the router initializes:

Configuring the RouterRollover cable – Console interface

Used to initially configure and troubleshoot a router.

Our rollover cables a DB9 connector at one end and do not need an adaptor.

Hyper terminal

Set up the PC’s serial port as follows:

• Bits per second: 9600 bps• Data bits: 8• Parity: None• Stop bits: 1• Flow control: None

Match serial port on PC

Backing Up Configuration Files – Capture Text

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Using Hyper Terminal

Examining the initial router bootup

Configuring the Router remotely - AUX

Auxiliary (AUX) Interface: Used for remote management of a Cisco router. Typically, a modem is connected to the AUX interface for dial-in access.

Telnet

Used to remotely access and configure a device (host, router, switch). To configure a remote router , it should have an active interface with an (IP

address). A connection using Telnet is called a Virtual Terminal (VTY) session, or connection. Telnet access devices using the command line interface (CLI). Configuring routers using Telnet should be protected through authentication.

ServerTelnet

Telnet

Power-up the router (and switch) – No configuration

If the routers do not have a saved configuration. After several lines of information on the screen you should eventually see:

Would you like to enter the initial configuration dialog? [yes/no]: n

Always answer “n” fo no. We will never be using setup mode. If you accidentally press “y” and enter Setup Mode, press and hold down the control

key and press C (CTRL-C). Wait a few seconds, and then press Enter.

On some routers you may see the following message.

Would you like to terminate autoinstall? [yes/no]: y

<There will be several lines of output>

Router>

Configuration Files

The configuration that defines the desired functionality of a Cisco device.

Two types of configuration files:

Start up configuration :

• Stored in the Non-Volatile RAM (NVRAM) . • Used as the backup configuration . • If configured , it is loaded to the RAM as the router boots or reloads o be

running configuration .

Running configuration

• Changes in running config will be parsed (translated , executed and take effect) by the Cisco IOS immediately or as the system boots.

• Should be saved to be included in the startup – config.• A configuration file may also be stored remotely on a server as a backup.

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The CLI uses a hierarchical structure for the modes.

The mode is identified by the prompt that is unique to that mode.

Each mode is used to accomplish particular tasks and has a specific set of commands that are available when in that mode.

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User Exec Mode

At the top of the modal hierarchical structure and the It is the first entrance into the CLI of an IOS router that allows only a limited

number of basic monitoring commands. Often referred to as view-only mode It is identified by the CLI prompt that ends with the > symbol. Ex: Router> Switch> By default, there is no authentication required to access the user EXEC mode

from the console.

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Privileged Exec Mode

For configuration and management commands. Also called the enable mode. It can be identified by the prompt ending with the # symbol. Ex: Router# Switch# The enable and disable commands are used to change the CLI between the

user EXEC mode and the privileged EXEC mode, respectively.

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Getting Help (Router and Switch)

Router> ? Exec commands: access-enable Create a temporary Access-List

entry access-profile Apply user-profile to interface clear Reset functions <text omitted> ping Send echo messages ppp Start IETF Point-to-Point Protocol

(PPP) --More--

• Press the Space Bar to scroll a “screen’s worth” of more commands.

• Press the Enter or Return key to scroll down just one line of the list.

• Press any other key to halt the list output.

Router>enaRouter#configure terminal <Must be in privileged mode>Enter configuration commands, one per line. End with CNTL/Z.Router(config)#?Configure commands: access-list Add an access list entry <text omitted>

Router(config)#exit00:03:20: %SYS-5-CONFIG_I: Configured from console by con

Router#config tEnter configuration commands, one per line. End with CNTL/Z.

Router(config)#exit00:03:34: %SYS-5-CONFIG_I: Configured from console by consoleRouter#

Hostname

Router#config tRouter(config)#hostname R1R1(config)#

• Changes the name, the prompt on the router.• Very important to do early on so you don’t get confused about which router you

are configuring.

Configuring router passwords

Not recommended, clear text

Router(config)#enable secret <password>

Use this command instead, password is encryped

Encrypts the passwords above, but…

Limiting Device Access

Every device should have locally configured passwords to limit access. The passwords introduced here are:

- Console password - limits device access to the console connection.- Enable password - limits access to the privileged EXEC mode.- Enable secret password - encrypted, limits access to the privileged EXEC mode.- VTY password - limits device access using Telnet

57You will see meaningless charactersIn config file

running-configRouter#show running-configCurrent configuration : 542 bytes!version 12.2!interface FastEthernet0/0 no ip address shutdown duplex auto speed auto!interface Serial0/0 no ip address shutdown!line con 0line aux 0line vty 0 4!endRouter#

• This current configuration file stored in the RAM memory. “lost when the router loses power or reloads”

• Privilege mode command.

• Can be reached only from privilege mode because they display password information.

Startup-config

Router#show startup-configstartup-config is not presentRouter#

• This file is the configuration file saved in NVRAM.

• If it exists in the NVRAM , it is copied into running-config as the router boots up.

• The router uses the running-config that should be saved to startup config from time to time.

Copy running-config to startup-config

Router#copy running-config startup-configDestination filename [startup-config]? <Press Enter>Building configuration...[OK]Router#show startup-configCurrent configuration : 542 bytes!version 12.2!interface FastEthernet0/0<text omitted>

Router# copy running-config startup-configORRouter# copy run start

Erase startup-config

Router#erase startup-configErasing the nvram filesystem will remove all files!

Continue? [confirm] <Press Enter>[OK]Erase of nvram: completeRouter#Reload

• When you are done with the routers in the lab, please be sure to erase the startup-config.

• If you are starting a lab, and you do not get the message:

Would you like to enter the initial configuration dialog?

[yes/no]: • You will need to erase the startup-config and reboot. • Privilege mode command.

Configuring an Ethernet interface

Router#conf tEnter configuration commands, one per line. End with CNTL/Z.Router(config)#inter fastethernet 0/0Router(config-if)#ip add 172.30.1.1 255.255.255.0Router(config-if)#no shutdownRouter(config-if)#endRouter#

• Your interfaces may differ.• Adding an IP address and subnet mask• no shutdown – turns on the interface.

Configuring Router Serial Interfaces

Serial interfaces are used to connect WANs to routers at a remote site or ISP.

If a DCE device such as a CSU/DSU is used , it will provide the clock. By default, Cisco routers are DTE devices, but they can be configured as DCE devices.

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Troubleshooting

172.30.1.20 172.30.1.25

Ping is the best way to test layer 3 connectivity

Ping uses the ICMP protocol to check for connectivity.

ping ip address i.e “ping 172.30.1.25”

The ping commandPings may fail

Test the Stack

Test 1: Local Loopback (ping 127.0.0.1)– successful, host 1 has the IP stack properly configured.

Test 2: Local NIC (ping own ip address) –

Test 3: Ping Local Gateway (192.168.23.254) – successful, The default gateway is operational. This also verifies the operation of the local network.

Test 4: Ping Remote Host (192.168.11.1) – failed, the problem probably appears to be somewhere beyond the local network.

Test 5: Traceroute to Remote Host (192.168.11.1) - Failure at First Hop

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Tracert , is used to trace the probable path a packet takes between source and destination.

Trace will show the path the packet takes to the destination, but the return path may be different.(Internet is an example)

• Uses ICMP message within an IP Packet

• Both are layer 3 protocols.

Trace (Traceroute)

Testing Sequence - Putting it all Together

C:\>tracert 192.168.11.1

Tracing route to 192.168.11.1 over a maximum of 30 hops  1 * * * Request timed out.  2 * * * Request timed out.  3 ^C**** the possible problem might be the default gateway setting in host

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RTA# traceroute 192.168.10.2

Traceroute uses ping (echo requests) Traceroute sets the TTL (Time To Live) field in the IP Header, initially to “1”

Trace

10.0.0.0/8 172.16.0.0/16 192.168.10.0/24

.1 .1 .1.2 .2 .2

DA = 192.168.10.2, TTL = 1

ICMP Time Exceeded, SA = 10.0.0.2

RTA RTB RTC RTD

RTB - TTL:

When a router receives an IP Packet, it decrements the TTL by 1. If the TTL is 0, it will not forward the IP Packet, and send back to the source an

ICMP “time exceeded” message.

Broadcast and network addresses , make sure these are not given to hosts.

The router interface IP here is a wrong IP since it represents the subnetwork address for all devices on the network.

Example: Sales department can’t get to ServerA in the mark. The client said she can ping the gateway. By looking at the figure, can you determine the problem?

  By looking at the figure, you can determine

that the default gateway on the Lab_B router is incorrect. That address is the broadcast address of the 64 subnet, so there’s no way it could be a valid host.

95 is 010 11111

Example: A user in the Sales LAN can’t get to ServerB. Using ping , the host can communicate to the local network but not to the remote network. Find and define the IP addressing problem.

Solution: ServerB has been configured with the broadcast address of the subnet. It is 01010111

show ip interface command

A serial interface will not show “up” and “up” unless both ends are properly configured (mostly) and a the no shutdown command is used.

If one router’s configuration looks okay, check the other router’s configuration.

Router# show ip interface brief Interface IP-Address OK? Method Status ProtocolEthernet0 131.108.1.11 YES manual up up Serial0 198.135.2.49 YES manual administratively down down

What is wrong here? The administrator has either done a “shutdown” on the interface or has forgotten to do a “no shutdown”.

Up or down

Interface status: Layer 1

• Up• Down• Administratively down (no shutdown to bring up)

Protocol: Layer 2

• Up• Down (no keepalive signal received)