Networking pt 2

Question 1

What does an IP/netmask pair let you identify?

hint: 2 parts

Answer 1

let’s you identify the network part and the host part of an IP address

Question 2

how many bits is IPv6?
what parts is it split in half for?
what does it have that is different from ipv4?

Answer 2

• 128 bit address
• 16 bit hexadecimal numbers
• separated by colon (:)
• split in half (64 bit each) for network part and device part
• dedicated subnet portion (unlike ipv4)

Question 3

What are the 3 IPv6 Address Types?

hint: G, U, L

Answer 3

• Global Unicast Address (global)
• Unique Local (internal)
• Link Local (internal

Question 4

What does a Router connect?

What does a Router forward?

Answer 4

• devices connected to different networks at the same time

- forward IP datagrams from one network to another

Question 5

What is a Router forwarding policy based on?
What does the policy determine?
What does it use to make a decision?

Answer 5

based on routing protocols - determines best path to reach a network using routing table

Question 6

What is the Routing default address?

When is it used?

Answer 6

0. 0.0.0

- used when router receives packet whose destination is an unknown network

Question 7

Where else does packet forwarding happen?

hint: which layer?

Answer 7

Lowest layer of TCP/IP stack: Link layer

Question 8

What are Hubs and Switches?
(hint: what do they forward and where?)

Which address do they work with?

Answer 8

• Devices that forward frames on local network

- work with MAC addresses

Question 9

Frames

Answer 9

Layer 2 packets

Question 10

MAC addresses

Answer 10

Media Access Control

• uniquely identify network card
• layer 2
• aka: physical address
• 48 bit (6 bytes)
• hexadecimal
• Linux ( ip addr), Windows (ipconfig), Mac (ifconfig)

Question 11

IP addresses

Answer 11

Layer 3 (network layer)
-address scheme to identify host in a network

Question 12

Using IP and MAC addresses, how will workstation A send a packet to workstation B?

Answer 12

• Datagram IP header: destination IP of workstation B
• Link layer header: destination MAC of router
• Source IP and source MAC of workstation A

Question 13

What happens after the router receives the packet from workstation A?

Answer 13

The router rewrites the MAC addresses but IP addresses stay the same:

• destination MAC: workstation B
• source MAC: router

Question 14

Forwarding Table/ CAM Table

Answer 14

• Content Addressable Memory Table
• Stored in devices RAM
• Used by switches to bind a MAC address to an interface

Question 15

How many ports do switches have?

Answer 15

Home: 4
Corporate: 64

Question 16

Network segmentation

Answer 16

• segmented by routers (not switches)

- routers DO NOT forward packets with Broadcast MAC address

Question 17

TTL

Answer 17

• Time To Live
• determines how long an entry will stay in the table
• bc CAM tables have a finite size

Question 18

How do switches decide which interface to use?

Answer 18

They identify new MAC/hosts dynamically with each new packet header and use the source MAC to decide which interface when forwarding.

Question 19

What happens to the CAM table when a switch encounters a MAC address?

Answer 19

• if MAC is not in table = creates a new MAC-interface binding
• if MAC is in table = updates TTL
• if MAC is in table and already binded to another interface = the table is updated

Question 20

Explain how forwarding happens.

Answer 20

1. switch reads destination MAC address of frame
2. performs CAM table lookup
3. forwards packet to corresponding interface
4. if no corresponding MAC address found, switch forwards to all interfaces