Eng. Ashraf presentation for the academy exam

Report
For the courtesy of others…

1
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) .




2
T1, DS3, OC3
PPP, HDLC
Frame Relay, ATM
ISDN, POTS
Communication starts with a
an application
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 .
Protocol Data Units and Encapsulation – another example
Segmentation and Encapsulation
Email Message
Data
Data
Data
Header
Data
Header
Header
Data
Data
Trailer
0010100111011001010000011111010100010101
Protocol Data Units and Encapsulation
Decapsulation and Reassembly
Email Message
Data
Data
Data
Header
Data
Header
Header
Data
Data
Trailer
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.
IP Addresses – First look
Network Address 172.16.0.0
172.16.10.100/16
Network Address
192.168.1.0/30
ISP
172.16.10.55/
16
Internet
192.168.1.2/30 172.16.1.1/16
192.168.1.1/30
C:\> ipconfig
Windows IP Configuration
Ethernet 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
8
172.16.10.3/1
6
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.
9
Domain Name System (DNS)
2
1
www.cisco.com
3
www.cisco.com = 198.133.219.25
•
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.
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
192.168.25.25
Subnet Mask
255.255.255.0
Default Gateway
192.168.25.1
DNS Server
208.67.222.222
Name Resolution
Need the IP address
DNS queries are two types of queries:
Recursive queries

Queries performed by Host to Local DNS Server
Iterative queries

12
Queries performed Local DNS server to other servers
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
Source Address
Destination Address
209.67.102.55

107.16.4.21
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.
15
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.
16
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
dynamically
using DHCP.
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.
18
IP Packets: Carrying Data End to End
•
Host X sends a packet to Host Y.
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.
Glass or plastic
fibers
Wireless Transmission
Metallic wires
within cables
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
Ethernet 802.3
Ethernet
802.2
Logical
Link
Control
(LLC)
802.3
Media
Access
Control
(MAC)
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
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.
Cabling – Show the straight-through and cross-over cables
Straight-through cable
Cross-over cable
router
switch
hub
26
hub
switc
h
hub
hub
hub
hub
switch
or hub
Intermediary
Devices
switch
or hub
routers
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.
27
Serial 0
192.168.10.1
255.255.255.252
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.
172.16.1.1
255.255.255.0
MAC: 0cddeeffaabb
Ethernet 0
172.16.2.1
255.255.255.0
MAC: 0abbccddeeff
Ethernet 1
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.
30
Routing – First Look
Network 192.168.1.0/24
Destination
Network
Next Hop
Network 192.168.2.0/24
192.168.1.254/24
Metric
C
192.168.2.0/24 is direction connected, FastEthernet0/1
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)
31
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
Data for Host
10.1.2.2 / 24
L2
IP TCP
DATA
Network 10.1.1.0
L2
IP TCP
DATA
Network 10.1.2.0
IP Address 10.1.2.2 is on
network 10.1.2.0
L2
IP TCP
DATA
L2
Packet Forwarding: Default Route
Data for Host
207.1.1.1 / 24
L2
IP TCP
DATA
Network 10.1.1.0
L2
IP TCP
DATA
Network 10.1.2.0
IP Address 207.1.1.1 is
on network 207.1.1.0
L2
IP TCP
DATA
L2
Packet Forwarding: Route Not Found
?
Data for Host
207.1.1.1 / 24
L2
IP TCP
DATA
Network 10.1.1.0
L2
IP TCP
DATA
Network 10.1.2.0
IP Address 207.1.1.1 is
on network 207.1.1.0
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.
36
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
Flash
Permanent.
Holds POST, boot instructions,
basic IOS.


NVRAM


Keeps contents
Holds startup configuration file
Keeps contents
Holds one or more IOS images


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 Router
Rollover 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.
Match serial port
on PC
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
Backing Up Configuration Files – Capture Text
Using Hyper Terminal
44
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
Telnet
Server
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.
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.
49
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.
50
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.
51
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.
52
Getting Help (Router and Switch)
Router> ?
Exec commands:
access-enable
entry
access-profile
clear
<text omitted>
ping
ppp
(PPP)
--More-•
•
•
Create a temporary Access-List
Apply user-profile to interface
Reset functions
Send echo messages
Start IETF Point-to-Point Protocol
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>ena
Router#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)#exit
00:03:20: %SYS-5-CONFIG_I: Configured from console by con
Router#config t
Enter configuration commands, one per line.
End with CNTL/Z.
Router(config)#exit
00:03:34: %SYS-5-CONFIG_I: Configured from console by console
Router#
Hostname
Router#config t
Router(config)#hostname R1
R1(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
Encrypts the
passwords above,
but…
Use this command instead, password is encryped
Router(config)#enable secret <password>
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
You will see meaningless characters
In config file
57
Router#show running-config
Current 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 0
line aux 0
line vty 0 4
!
end
Router#
running-config
•
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-config
startup-config is not present
Router#
•
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 runningconfig that should be saved
to startup config from time
to time.
Copy running-config to startup-config
Router# copy running-config startup-config
OR
Router# copy run start
Router#copy running-config startup-config
Destination filename [startup-config]? <Press Enter>
Building configuration...
[OK]
Router#show startup-config
Current configuration : 542 bytes
!
version 12.2
!
interface FastEthernet0/0
<text omitted>
Erase startup-config
Router#erase startup-config
Erasing the nvram filesystem will remove all files! Continue?
[confirm] <Press Enter>
[OK]
Erase of nvram: complete
Router#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 t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#inter fastethernet 0/0
Router(config-if)#ip add 172.30.1.1 255.255.255.0
Router(config-if)#no shutdown
Router(config-if)#end
Router#
•
•
•
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.
63
Troubleshooting
The ping command
Pings may fail
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”
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
66
Trace (Traceroute)


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.
67
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
68
Trace
10.0.0.0/8
172.16.0.0/16
RTA
RTB
.1
.2
192.168.10.0/24
RTC
.1
.2
RTD
.1
.2
DA = 192.168.10.2, TTL = 1
ICMP Time Exceeded, SA = 10.0.0.2
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”
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
Router# show ip interface brief
Interface
Ethernet0
Serial0
IP-Address
131.108.1.11
198.135.2.49
OK?
YES
YES
Method
manual
manual
Status
up
administratively down
Protocol
up
down
What is wrong here? The administrator has either done a
“shutdown” on the interface or has forgotten to do a “no shutdown”.


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.
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)

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