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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. - PowerPoint PPT Presentation
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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
14 End devices
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)