Számítógép networkok gyakorlata

172 .
16 .
254 .
1
10101100 .
00010000 .
11111110 .
00000001
• Logical addressing
• 32 bit integer
• IP address can be split into two parts: network and host ID

• Network ID is the same at each host inone network. Host ID has to be different
• Routers use the network ID when forwarding packages.
• One host can have multiple interfaces – each interface connects to a different network

• Back in the dark ages the first 8 bits were the network ID, the rest was the host id
• It was realized soon how smal that number is.
• In 1981 the Classful Network achitecture was created. It described 5 classes that were self explanatory from the IP address (A, B, C,
D, E
)
• Scalability was an issue even using this architecture, so in 1993 ”Classless Inter-
Domain Routing” (CIDR) architecture was invented which uses variable length network ID

A class
B class
C class
D class
E class
0
1 0
1 1 0 network
1 1 1 0
1 1 1 1 0
Classful Network host network network multicast reserved host host
Class Leading bits First octet
A class 0
B class 10
C class 110
D class 1110
E class 11110
0 – 127
128 – 191
192 – 223
224 – 239
240 – 255
Number of networks
2 7 = 128
Number of hosts
2 14 = 16.384
2 24 = 16.777.216
2 16 = 65.536
2 21 = 2.097.152
2 8 = 256
–
–
–
–

• Often it is necessary to connect devices to the network, but not to the internet. RFC 1918 manages the private IP addresses that cannot appear on the internet, but are reserved for private use.
• Private IP ranges managed by IANA:
Class From To No. Of hosts
1 x A class 10.0.0.0
10.255.255.255 2 24 = 16.777.216
16 x B class 172.16.0.0
172.31.255.255 2 20 = 1.048.576
256 x C class 192.168.0.0 192.168.255.255 2 16 = 65.536
• example:
- 192.168.1.0/24 (mask: 255.255.255.0 | 256 hosts) - 256 networks
- 172.17.0.0/16 (mask: 255.255.0.0 | 65.536 hosts) 256 networks

• Sometimes it is necessary for hosts to provide services that have to be used by itself.
• Such services are provided through the loopback network.
• The loopback device is implemented in software only
• Canniot appear on the web
• Speciális címe a localhost ami a 127.0.0.1 IP cím.
address last network address number of hosts
1 x A class 127.0.0.0 127.255.255.255 2 24 = 16.777.216

• networki cím:
IP address full of zeroes
– xx.xx.xx.0
• Broadcast cím:
IP address full of ones
– xx.xx.xx.255

• Further subcategorize the network
• 32 bit number

• 192.168.0.0/24 [mask: 255.255.255.0] network id range Broadcast addr.
Állomások száma
192.168.0.0
192.168.0.1 – 192.168.0.254 192.168.0.255
• 192.168.0.0/22 [maszk: 255.255.252.0] network id range Broadcast addr
253
Állomások száma
192.168.0.0
192.168.0.1 – 192.168.3.254 192.168.3.255
• 192.198.0.0/26 [maszk: 255.255.255.192]
1022 network id
192.168.0.0
range Broadcast addr
192.168.0.1 – 192.168.0.62
192.168.3.63
Állomások száma
61

• Unicast:
Egy az egynek kapcsolat
Minden cím egyedi és központilag kiosztott, emiatt egyértelműen azonosítja a címzettet.
• Multicast:
Egy a többnek kapcsolat
Lehetővé teszi az adó számára, hogy az üzenete több címzetthez is eljusson.
• Broadcast:
Egy mindenkinek kapcsolat
A multicast speciális esete, ekkor mindenkinek szól az
üzenet, így a network összes eleme beolvassa a csomagot.