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Introduction to Networking > 5. Network Layer > Flashcards

5. Network Layer Flashcards

1
Q

What is the purpose of the network layer?

A
  1. Provide services to allow end devices to exchange data
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2
Q

List out the 2 types of pricinple network layer communcation protocols

A
  1. IPv4
  2. IPv6
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3
Q

List out the 4 basic operations

A
  1. Addressing End Devices
  2. Encapsulation
  3. Routing
  4. De-encapsulation
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4
Q

What does IP encapsulates ( Which Layer )?

A
  1. Transport Layer Segment
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5
Q

IP can use what packet and not impact the layer 4 ( Transport Layer ) segmant? ( 2 )

A
  1. IPv4
  2. IPV6
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6
Q

What is a dual stack network?

A
  1. A network that is using both IPv4 and IPv6
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7
Q

What layer will examine IP packet as it traverses the network?

A
  1. Layer 3 devices
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8
Q

Will IP addressing change from source to destination?

A
  1. No
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9
Q

What can change addressing?

A
  1. NAT
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10
Q

What is the characteristics of IP? ( 3 )

A
  1. Connections
  2. Best Effort
  3. Media Independent
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11
Q

Why IP is connectionless? ( 4 )

A
  1. Doesn’t establish a connection with the destination before sending the packet
  2. There is no control information needed ( synchronizations, acknowledgements )
  3. The destination will receive the packet when it arrives, but no pre-notifications are sent by IP
  4. If there is a need for connection-oriented traffic, then another protocol wil handle this
  • TCP will handle it
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12
Q

Why IP is best effort? ( 4 )

A
  1. IP will not guarantee deliery of the packet
  2. IP has reduced overhead since there is no mechanism to resend data that is not received
  3. IP does not expect acknowledgements
  4. IP does not know if the other devive is operational or it recived the packet
  • Overhead - The information must be sent with the payload
  • Payload - Actual Data
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13
Q

Why IP is media independent?

A
  1. IP does not concern itself with the type of frame required at the data link layer or the media type at the physical layer
  2. IP can be sent over any media type ( copper, fiber or wireless )
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14
Q

Why IP is unreliable?

A
  1. It cannot be manage or fix undelivered or corrupt packets
  2. IP cannot retransmit after an error
  3. IP cannot realign out of sequence packets.
  4. IP must rely on other protocols ( TCP ) for these functions
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15
Q

What will network layer establish?

A
  1. Maximum Transmission Unit ( MTU )
  • At Transport Layer Slides
  • 1500 bytes
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16
Q

What is the step of network layer when establishing MTU ( Maximum Transmission Unit ) ?

A
  1. Network layer receives this from control information sent by the data link layer
  2. The network then established the MTU size
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17
Q

What is fragmentation in layer 3?

A
  1. Splits the IPv4 packet into smaller units
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18
Q

Will fragmenting causes latency?

A
  1. Yes
  • IPv6 does not fragment packets
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19
Q

What is the purpose of network header ? ( 3 )

A
  1. It ensures the packet is sent in the correct direction ( to the destination )
  2. It contains information for network layer processing in various fields.
  3. The information in the header is used by all layer 3 devices that handle the packet
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20
Q

List out the IPv4 network header characteristics

A
  1. It is in binary
  2. Contains several fields of information
  3. Diagram is read from left to right, 4 bytes per line
  4. The 2 most important fields are the source and destination
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21
Q

List out the 3 major limitations of IPv4

A
  1. IPv4 address depletion
    • Basically run out of IPv4 addressing
  2. Lack of end-to-end connectivity
  3. Increased network complexity
    • NAT creates issues on the network as a side effect of manipulating the network headers addressing
    • NAT causes latency and troubleshooting issues
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22
Q

How to let IPv4 survive? ( 2 )

A
  1. Private Addressing
  2. NAT
23
Q

What ended when private addressing and NAT were created?

A
  1. Direct communications with public addressing
24
Q

What is NAT meant for? What is the side effects

A
  1. Tempory solution for IPV4 to create issues on the network as a side effect of manipulating the network headers addressing
  2. NAT causes latency and troubleshooting issues.
25
Q

Who developed IPv6?

A
  1. IETF ( Internet Engineering Task Force )
  • IPv6 overcomes the limitations of IPv4
26
Q

List out the improvements that IPv6 provides ( 3 )

A
  1. Increased address space
    • Based on 128 bit address, not 32 bits
  2. Improved packet handling
    • Simplified header with fewer fields
  3. Eliminates the need for NAT
    • Since there is a huge amount of addressing, there is no need to use private addressing internally and be mapped to a shared public address
27
Q

What is the fixed bytes of the header in IPv6?

A
  1. Fixed at 40 bytes or octets long
  • It is simplified, but not smaller
28
Q

What is removed to improve performance?

A
  1. Several IPv4 fields
29
Q

What things in IPv4 fields were removed to improve performance? ( 3 )

A
  1. Flag
  2. Fragment Offset
  3. Header Checksum
30
Q

IPv6 packet may also contain what?

A
  1. Extension Headers ( EH )
31
Q

What is the Extension Headers ( EH ) characteristics? ( 4 )

A
  1. Provide optional network layer information
  2. Are optional
  3. Are placed between IPv6 header and the payload
  4. May be used for fragmentation, security, mobility support
32
Q

Will IPv6 packets be fragmented?

A
  1. No
33
Q

What are always created at the source?

A
  1. Packets
  • Each host device creates their own routing table
34
Q

What does a packets contain when a host send it?

A
  1. Its own IP address ( IPv4 or IPv6 )
  2. Local Hosts ( Destination on the same LAN )
  3. Remote Hosts ( Devices are not on the same LAN )
35
Q

What device will determine whether the destination is local or remove?

A
  1. The source device
36
Q

Show the determination method of how the source device determines the destination is local or remove ( 2 )

A
  1. IPv4
    • Source uses its own IP address and Subnet mask, along with the destination IP
  2. IPv6
    • Source uses the network address and prefix advertised by the local router
37
Q

What will happen when the destination is remote ?

A
  1. Local traffic is dumped out the host interface to be handled by an intermediary device
  • Uses default gateway ( routers ) on the LAN to send the data
38
Q

Which can be a default gateway? ( 2 )

A
  1. A router
  2. Layer 3 Switch
39
Q

List out the features of default gateway ( 3 )

A
  1. It must have an IP address in the same range as the rest of the LAN
  2. It can accept data from the LAN and is capable of forwarding traffic off the LAN.
  3. It can route to other networks
40
Q

What will happen if a device has no default gateway or a bad default gateway?

A
  1. Its traffic will not be able to leave the LAN
41
Q

How does the host know the default gateway ( DGW ) ? ( 2 )

A
  1. Statically
  2. Through DHCP in IPv4
42
Q

How does devices know the default gateway by using IPv6?( 2 )

A
  1. Configured Manually
  2. Router Solicitation ( RS )
43
Q

What will the default gateway be configured when there is no more route in the routing table?

A
  1. Is a static route which will be a lost resort route in the routing table
44
Q

What will be needed if the device intend to send traffic remotely?

A
  1. Default gateway for all the device on the LAN
45
Q

How can we print the routing table on our computer?

A
  1. netstat -r
46
Q

What will the netstat -r show ? ( 3 )

A
  1. Interface Unit
    • All pottential interfaces
    • MAC addressing
  2. IPv4 Routing Table
  3. IPv6 Routing Table
47
Q

What happens when the router receives the frame from the host device? ( 5 )

A
  1. Packet arrives on the Gigabit Ethernet 0/0/0 interface of router R1.
  2. R1 de-encapsulates the Layer 2 Ethernet header and trailer
  3. Router R1 examines the destination IPv4 address of the packet and searches for the best match in its IPv4 routing table
  4. The route entry indicates that this packet is to be forwarded to router R2
  5. Router R1 encapsulates the packet into a new Ethernet header and forwards the packet to the next hop router R2
48
Q

List out the 3 types of router in a router’s routing table

A
  1. Directly Connected
    • These routes are automatically added by the router
    • Provided interface isactive and has addressing
  2. Remote
    • These are the router that doesn’t have direct connection
    • Manually , with a static route
    • Dynamically , using a routing protocol to have the routers share their information with each other
  3. Default Route
    • Forwards all traffic to a specific direction when there is not a match in the routing table
49
Q

What is the characteristics of static routing? ( 4 )

A
  1. Must be configured manually
  2. Must be adjusted manually by the administrator when there is a change in the topology
  3. Good for small non-redundant networks
  4. Often used in conjuction with a dynamic routing protocol for configuring a default route
50
Q

What is the characteristics dynamic routes ? ( 4 )

A
  1. Discover remote networks
  2. Maintain up-to-date information
  3. Choose the best path to the destination
  4. Find new best paths when there is a topology change
51
Q

Can dynamic routing share static default routes with other routers?

A
  1. Yes
52
Q

How to let switch shows IPv4 routing table ?

A
  1. show ip route
53
Q

List out the route sources ( 5 )

A
  1. L - Directly connected local interface IP address
  2. C - Directly connected network
  3. S - Static route was manually configured by an administrator
  4. O - OSPF
  5. D - EIGRP
54
Q

What does the show ip route shows? ( 3 )

A
  1. Directly connected - C and L
  2. Remote routes - O, D, etc.
  3. Default routes - S*

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