Layer 3 (Nätverkslagret)

Question 1

What is the main purpose of the network layer(Layer 3)?

Answer 1

The network layer is responsible for packet forwarding including routing through intermediate routers.

Question 2

What functions does Layer 3 have?

Answer 2

• Adressering av “end devices” (unika IP-addresser)
• Encapsulation (IP headers)
• Routing
• De-encapsulation

Question 3

What protocols are used in Layer 3?

Answer 3

IPv4, IPv6

Question 4

What does it mean when we say IP is connectionless?

Answer 4

Sändare vet inte om mottagaren är närvarande, eller om paketen nåde destination.

Question 5

What does it mean when we say that IP is media-independent?

Answer 5

IP fungerar oberoende av mediatyp (wireless, fiber, serial…)

Question 6

How many bytes is an IP header?

Answer 6

20 bytes

Question 7

What are important fields in an IP header?

Answer 7

• Version - What IP-version is used? (IPv4 or IPv6)
• TTL (Time to Live)
• Protocol
• Source/Destination IP

Question 8

What is the loopback address?

Answer 8

127.0.0.1

Question 9

What is the loopback address used for?

Answer 9

Packets sent to this address never reach the network but are looped through the network interface card only. This can be used for diagnostic purposes to verify that the internal path through the TCP/IP protocols is working.

Question 10

What kind of memory does the router have?

Answer 10

• Volatile memory (RAM) → Kräver konstant spänning → statisk information
• Non-volatile memory (ROM) → Klarar spänningsavbrott → startup-config