IPv4 addressing (1)
Network layer
OSI Model & TCP-IP Suite#3 Network layer
Routing
IP addresses are logical addresses you assign when you configure the device.
Switches do not separate differenet networks. They connect and expand networks.
Even if you have multiple PCs and Switches connected, they'd still belong to one network/LAN.
Because of this, all PCs have IP addresses in the same Layer3 network 192.168.1.0/24 (PC1 - 192.168.1.1, PC2 - 192.168.1.2).
If you put a Router in between 2 switches, the network is split into 2 networks (192.168.1.0/24, 192.168.2.0/24).
Router needs IP address for each network it is connected to.
Now if PC1 sends a broadcast frame, the switch receives it and forwards it out to all interfaces (except the one it received from).
Switch sends the frame out of G0/1 and G0/2, and PC1 and Router receive the frame. It ends there.
Broadcast is limited to the local network.
IPv4
Intro
Internet Protocol (IP) is the primary Layer3 protocol in use today and v4 (version 4) is the one used in most networks.
IP addresses are 32 bits (4 bytes) in length.
Decimal, Hex, Binary
Decimal (base 10) : 3294 (3* 1000 + 2* 100 + 9* 10 + 4* 1 = 3294)
Hexadecimal (base 16) : CDE (12* 256 + 13* 16 + 14* 1 = 3294)
Binary (base 2) : 192.168.1.254 = 11000000.10101000.00000001.11111110
These 8 bit groups are called octets.
Range of possible numbers that can be represented with 8 bits ranges from 0 to 255.
(Learn to convert Binary to Decimal and vice versa)
IPv4 address
IP addresses have 4 octets.
/24 at the end tells us first 3 octets (24 bits) represent the network and the last octet (8 bits) represents the end hosts (PCs).
IPv4 class
| Class | First octet | Numeric range | Prefix | Netmask | Networks | Addresses |
|---|---|---|---|---|---|---|
A | 0xxxxxxx | 0 - 127 | /8 | 255.0.0.0 | 2^7 (128) | 2^24 -2 (16m) |
B | 10xxxxxx | 128 - 191 | /16 | 255.255.0.0 | 2^14 (16k) | 2^16 -2 (65k) |
C | 110xxxxx | 192 - 223 | /24 | 255.255.255.0 | 2^21 (2m) | 2^8 -2 (255) |
Class A : **12.**128.251.23/8 (fewer network addresses, many hosts)
Class B : **154.78.**111.32/16
Class C : **192.168.1.**254/24 (many possible networks, fewer hosts)
| Class | First octet | Numeric range | Uses |
|---|---|---|---|
D | 1110xxxx | 224 - 239 | Multicast purposes |
E | 1111xxxx | 240 - 255 | Experimental purposes |
Class D - Multicast purposes.
Class E - experimental uses.
Loopback addresses
End of Class A is usually considered to be 126, not 127.
127 range - reserved for loopback purposes.
Range : 127.0.0.0 to 127.255.255.255
Used to test the 'network stack' of the local device.
If a device sends any network traffic to an address in this range, it is simply processed backup the TCP/IP stack as if it were traffic received from another device.
ping 127.0.0.1 or any address in the 127 range and your PC will respond to its own pings.
The round trip times will be 0ms because the traffic isn't going anywhere
Network address
First address in each network.
Cannot be assigned to a host.
Host portion on an IP address is all 0's.
Eg: 192.168.1.0/24
First usable address is the one above the network address (192.168.1.1)
Broadcast address
Layer3 address used to send a packet to all hosts on the local network.
Last address in a network.
Also, cannot be assigned to a host.
Host portion is all 1's.
Eg: 192.168.1.255/24
The last usable address is the one under the broadcast address (192.168.1.254)
If a packet is send with a broadcast IP address (192.168.1.255) as the destination IP address, the destination MAC address would be broadcast MAC address - all F's (FF.FF.FF.FF.FF.FF). If PC1 from above picture sent a ping to 192.168.1.255, it would be received by PC2 and R1's G0/0 interface.
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