Ccnav3 110 (arp) TRUYỀN SỐ LIỆU VÀ MẠNG

CCNA Semester 1

Chapter 10

LAYER 3

1

PROTOCOLS


LAYER 3 DEVICES
AND
NETWORK TO NETWORK

2

COMMUNICATION


3

}Internetworking


}Path determination

4

• Path determination is the process that the router
uses to choose the next hop in the path for the

packet to travel to its destination based on the
link bandwidth, hop, delay ...


}Router

• A router is a type of internetworking device that
passes data packets between networks, based on
Layer 3 addresses.

5

• A router has the ability to make intelligent
decisions regarding the best path for delivery of
data on the network.


}IP addresses

• IP addresses are implemented in software, and
refer to the network on which a device is located.
• IP addressing scheme, according to their
geographical location, department, or floor within
a building.

6

• Because they are implemented in software, IP
addresses are fairly easy to change.

7

}Router and Bridge


}Router connections

• Routers connect two or more networks, each of
which must have a unique network number in
order for routing to be successful.

8

• The unique network number is incorporated into
the IP address that is assigned to each device
attached to that network.


9

}Router Interface


10

}Router function


}Router function (cont.1)

Strips off the data link header,
carried by the frame.

11

(The data link header contains the
MAC addresses of the source and
destination.)


}Router function (cont.2)

12

Examines the network layer
address to determine the
destination network.


}Router function (cont.3)

13

Consults its routing tables to
determine which of its interfaces it
will use to send the data, in order
for it to reach its destination
network.

}Router function (cont.4)

14

Send the data out interface B1, the
router would encapsulate the data
in the appropriate data link frame.


}Router Interface example

• Interface is a router’s attachment to a network, it
may also be referred to as a port. In IP routing.

15

• Each interface must have a separate, unique
network address.


16

}IP address assignment

static addressing and dynamic addressing


}Static addressing

• You must go to each individual device and
configure it with an IP address.

17

• You should keep very meticulous records,
because problems can occur on the network if
you use duplicate IP addresses.


}Dynamic addressing

• There are a few different methods that you can
use to assign IP addresses dynamically:
– RARP: Reverse Address Resolution Protocol.
– BOOTP: BOOTstrap Protocol.

18

– DHCP: Dynamic Host Configuration Protocol.


}Dynamic addressing: RARP
RARP Request

RARP Reply

19

MAC: Known

IP:
Unknown

RARP server


}Dynamic addressing: BOOTP
UDP Broadcast

UDP Broadcast

20

MAC: Known
IP:
Unknown

IP Address
IP of server
Vendor--specific
Vendor

BOOTP server
MAC1 – IP
MAC1
IP1
1
MAC2
MAC
2 – IP

IP2
2
MAC3
MAC
3 – IP
IP3
3


}Dynamic addressing: DHCP
DHCP Discover
UDP Broadcast
DHCP Offer
UDP Broadcast
DHCP Request
DHCP Ack

21

MAC: Known
IP:
Unknown

IP Address
Gateway
IP of servers
And more …

DHCP server
IP1

IP1
IP2
IP
2
IP3
IP
3


22

ARP CONCEPT


23

}Encapsulation


}Address resolution protocol

24

• In order for devices to communicate, the sending
devices need both the IP addresses and the MAC
addresses of the destination devices.
• When they try to communicate with devices whose
IP addresses they know, they must determine the
MAC addresses.
• ARP enables a computer to find the MAC address

of the computer that is associated with an IP
address.


25

}Address resolution protocol