What types of addresses are used at the network layer?

At the network layer (L3), logical addresses are used, which allow data to be delivered between different networks. These addresses do not depend on a specific device or cable and can change.

Short version: the network layer uses IP addresses.

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#The main address type: IP addresses

#1. IPv4 addresses

The most common option.

• length: 32 bits
• notation: four numbers from 0 to 255

Example:

192.168.1.10

An IPv4 address consists of:

• a network part
• a host (device) part

From this address, routers understand:

• which network the destination is in
• where to forward the packet next

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#2. IPv6 addresses

A new standard created because of IPv4 exhaustion.

• length: 128 bits
• hexadecimal notation

Example:

2001:0db8:85a3::8a2e:0370:7334

IPv6:

• supports a huge number of addresses
• is actively used in modern networks and the Internet

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#Types of IP addresses by delivery method

At the network layer, addresses differ by who the data is intended for.

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#1. Unicast address

• the address of one specific device
• the most frequent option

Used when:

• a packet needs to be delivered to one recipient

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#2. Multicast address

• the address of a group of devices
• only those subscribed to the group receive the packet

Used for:

• streaming video
• service network protocols

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#3. Broadcast address (IPv4 only)

• the packet is sent to all devices in the network
• used for service tasks

Important:

• broadcast is not routed
• it exists only within a single network

IPv6 has no broadcast; multicast is used instead.

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#Public and private IP addresses

#Private

Used inside local networks:

• 192.168.0.0/16
• 10.0.0.0/8
• 172.16.0.0/12

Not routed directly to the Internet.

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#Public

• unique on the Internet
• used to access external resources

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#What is important for an interview

• the network layer uses IP addresses, not MAC
• an IP address:
  • is logical
  • can change
• a MAC address:
  • is physical
  • is used by the layer below (L2)

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#In short, for an interview

The network layer uses logical IP addresses (IPv4 and IPv6), which can be unicast, multicast, and (in IPv4) broadcast, and serve to deliver packets between networks.