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CCNA-ITN > 08 Network Layer > Flashcards

08 Network Layer Flashcards

1
Q

List the four basic processes of the network layer:

A
  1. Addressing end devices
  2. Encapsulation of L4 PDUs
  3. Routing packets toward their destination on another network
  4. De-encapsulation of the packet on arrival; hand-off of L4 PDU to transport layer
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2
Q

Consider a packet being sent between two devices on different networks. Does the packet’s IP addressing information change between hops?

A

The packet’s L3 addressing does not change between hops, unless network address translation is in use.

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3
Q

List the 3 characteristics of IP:

A
  1. Connectionless - no connection with destination established beforehand
  2. Best-effort - packet delivery not guaranteed
  3. Media-independent - the medium carrying the data does not matter
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4
Q

How does the network layer determine the MTU value?

A

The datalink layer passes the MTU value to the network layer. The network layer then determines how large packets can be.

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5
Q

What issue is created when a router must forward packets from one medium to another medium that has a smaller MTU value?

A

fragmentation

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6
Q

What is the result of fragmentation?

A

latency

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7
Q

IPv4 packets can be fragmented by routers. Can IPv6 packets be fragmented by routers?

A

no

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8
Q

This IPv4 packet field identfies the number of 32-bit words in the header

A

internet header length

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9
Q

This IPv4 packet field is used to determine the priority of the packet

A

DS, or differnetiated services

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10
Q

This IPv4 packet header field has a maximum value of 65,535 bytes

A

total length

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11
Q

What is the purpose of the identification, flag, and fragment offset fields in an IPv4 packet?

A

used to re-order a fragmented packet

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12
Q

What IPv4 packet field consists of an 8-bit value used to limit the lifetime of a packet?

A

TTL

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13
Q

What is the purpose of the identification, flag, and fragment offset fields in an IPv4 packet?

A

used to re-order a fragmented packet

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14
Q

What two tasks does a router perform each time it encounters an IPv4 packet?

when processing a packet, it does two things to fields within the packet

-

A
  1. decrements TTL value by 1
  2. recalculates header checksum
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15
Q

A router decrements the TTL of a packet from 1 to 0. What two tasks does it perform next?

A
  1. drops the packet
  2. sends ICMP Time Exceeded message to source IP address
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16
Q

What does a value of 1 indicate when found in the Protocol field of an IP packet?

A

Indicates that the packet is an ICMP packet.

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17
Q

What does a value of 6 indicate when found in the Protocol field of an IP packet?

A

Indicates the packet is a TCP packet

18
Q

What does a value of 17 indicate when found in the Protocol field of an IP packet?

A

Indicates the packet contains a UDP datagram.

19
Q

This IPv4 packet field is used to detect corruption within the IPv4 header

A

header checksum

20
Q

What is the purpose of the IPv4 packet fields internet header length, total length, and header checksum?

A

used to identify a validate an IPv4 packet

21
Q

What is a characteristic of the IPv4 source address packet field?

In other words, what is unique to this field?

A

it is always a unicast address

22
Q

What is a characteristic of the IPv4 destination address packet field?

in other words, what kind(s) of addresses can this field contain?

A

it can be a unicast, multicast, or broadcast address

23
Q

What are 3 limitations of IPv4?

A
  1. IPv4 address depletion
  2. lack of end-to-end connectivitiy (reliance on NAT)
  3. increased complexity imposed by NAT
24
Q

What 3 ways that IPv6 improves on IPv4?

A
  1. larger 128-bit address space
  2. simplified header (improves packet handling)
  3. removes need for NAT
25
Q

What is the IPv6 equivalent to the the IPv4 DS packet header field?

A

traffic class

26
Q

What IPv6 packet header field suggests that all packets with the same field value receive the same type of handling by routers?

A

flow label

27
Q

What IPv6 packet header field indicates the length of the packet data, but does NOT include the length of the entire header?

A

payload length

28
Q

What IPv6 packet header field is eqiuivalent to the IPv4 protocol field?

A

the “next header” field

29
Q

This IPv6 packet header field is equivalent to the IPv4 TTL field.

A

hop limit

30
Q

What is the length of the entire IPv6 header?

A

fixed at 40 bytes

31
Q

What is the value of the IPv6 version packet header field?

A

0110

32
Q

List the IPv4 and IPv6 loopback addresses

A

IPv4: 127.0.0.1

IPv6: ::1

33
Q

How does a host determine if a packet is local or remote (give answers for IPv4 and IPv6)

A

IPv4:

The source device compares its subnet mask and IP address with the destination IP address to make this determination.

IPv6:

The local router advertises the prefix of the local network to all devices.

34
Q

List three primary features of a default gateway:

A
  1. Route packets from one network to a remote network
  2. Has an IP address in the same range as other hosts on the local network
  3. Can forward data into or take data out of the local network
35
Q

List and describe the three types of routing entries found in a routing table:

A

Directly connected routes - routes generated by virtue of being associated with an interface (connected) and activated.

Remote routes - routes that are explicitly configured or learned by a dynamic routing protocol

Default routes - routes that are used as a last resort if no matching route is found in the routing table

36
Q

List and describe two ways a router learns about remote networks:

A
  1. Explicit configuration
  2. Learned via advertisement by a dynamic routing protocol
37
Q

What are the four characteristics of static routing?

A
  1. Static routes are manually configured
  2. Static routes must be manually changed if no longer valid
  3. Static routes are appropriate for small networks or those with few/no redundant links
  4. May be used in conjunction with dynamic routing for advertising default routes
38
Q

In considering the TCP/IP transport suite, at what layer does reliability reside?

A

Reliability in TCP/IP is at the transport layer.

39
Q

What IPv6 packet header field is eqiuivalent to the IPv4 protocol field?

A

the “next header” field

40
Q

The behavior of the IPv6 hop limit field is similar to that of the IPv4 TTL field, in that the field value is decremented by 1 each time the packet crosses a router. What is DIFFERENT about the behavior of an IPv6 packet as it crosses a router?

A

There is no need to recalculate the header checksum field as in IPv4 (the field does not exist). This improves performance of IPv6.

CCNA-ITN (11 decks)

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