Lesson 6 — CCNA module 8-13 Flashcards
1
Q
What does the network layer do in the OSI model?
A
The network layer performs four basic operations:
* Addressing end devices
* Encapsulation
* Routing
* De-encapsulation
2
Q
What are the two principle network layer communication protocols?
A
IPv4 and IPv6
3
Q
What is IP encapsulation?
A
IP encapsulation means wrapping an IP packet inside another IP packet
4
Q
What is exactly encapsulated during the IP encapsulation process?
A
IP encapsulates the transport layer
segment.
5
Q
Which IP versions can be used during encapculation?
A
IP can use either an IPv4 or IPv6
packet and not impact the layer 4
segment.
6
Q
Where is the packet IP examinated?
A
IP packet are examined by all
layer 3 devices as it traverses the
network
7
Q
Does the IP addressing change from source to destination?
A
No, The IP addressing does not change from source to destination.
8
Q
What are the different IPv4 network header characteristics?
A
- It is in binary.
- Contains several fields of information
- Diagram is read from left to right, 4 bytes per
line - The two most important fields are the source
and destination.
9
Q
What are the different IPv4 Packet Header Fields?
A
- Version
- Differentiated Services
- Header Checksum
- Time to Live (TTL)
- Protocol
- Source IPv4 address
- Destination IPv4 Address
10
Q
What is the Version IPv4 Packet Header Field?
A
This will be for v4, as opposed to v6, a 4 bit field= 0100
11
Q
What are the Differentiated Services IPv4 Packet Header Field?
A
Used for QoS: DiffServ – DS field or the older IntServ – ToS or Type of Service
12
Q
What is the Header Checksum IPv4 Packet Header Field?
A
It Detects corruption in the IPv4 header
13
Q
What is the TTL IPv4 Packet Header Field?
A
It’s the Layer 3 hop count. When it becomes zero the router will discard the packet.
14
Q
What is the Protocol IPv4 Packet Header Field?
A
I.D.s next level protocol: ICMP, TCP, UDP, etc.
15
Q
What is the Source IPv4 address IPv4 Packet Header Field?
A
32 bit source address
16
Q
What is the Destination IPV4 Address IPv4 Packet Header Field?
A
32 bit destination address
17
Q
How is IPv6 better thanIPv4?
A
IPv6 overcomes the limitations of IPv4
18
Q
What are the two main improvements that IPv6 provides
A
Increased address space and Improved packet handling
19
Q
What is the major design improvements of IPv6 over IPv4?
A
The IPv6 header is simplified,
but not smaller
20
Q
At how many bytes is the IPv6 Header fixed?
A
40 bytes (or octets)
21
Q
What are the IPv4 fields that have been removed to improve performance?
A
Flag, Fragment Offset and Header Checksum
22
Q
What are the different IPv6 packet headers?
A
- Version
- Traffic Class
- Flow Label
- Payload length
- Next Header
- Hop limit
- Source IPv4 Address
- Destination IPv4 Address
23
Q
What is the version IPv6 Packet Header Field?
A
This will be for v6, as opposed to v4, a 4 bit field= 0110
24
Q
What is the traffic class IPv6 Packet Header Field?
A
Used for QoS: Equivalent to DiffServ – DS field
25
What is the flow label IPv6 Packet Header Field?
It Informs device to handle identical flow labels the same way, 20 bit field
26
What is the payload length IPv6 Packet Header Field?
This 16-bit field indicates the length of the data portion or payload of the IPv6
packet
27
What is the Next Header IPv6 Packet Header Field?
I.D.s next level protocol: ICMP, TCP, UDP, etc.
28
What is the Hop Limit IPv6 Packet Header Field?
Replaces TTL field Layer 3 hop count
29
What is the Source IPv4 Address IPv6 Packet Header Field?
128 bit source address
30
What is the Destination IPV4 Address IPv6 Packet Header Field?
128 bit destination address
31
What is Host Forwarding Decision?
It's the process where a device (host) determines how to send a packet of data to its destination, based on information in its routing table
32
Where are the packets created?
With both IPv4 and IPv6, packets are always created at the source host.
33
What does each host device create during the Host Forwarding Decision process?
Each host devices creates their own routing table
34
To who can the hosts send packets to?
- Itself – 127.0.0.1 (IPv4), ::1 (IPv6)
- Local Hosts – destination is on the same LAN
- Remote Hosts – devices are not on the same LAN
35
What is a default gateway?
It's a router or a layer 3 switch that directs network traffic from a local network to other networks, including the internet, when no other route is specified.
36
What are the different features a default gateway has?
- It must have an IP address in the same range as the rest of the LAN.
- It can accept data from the LAN and is capable of forwarding traffic off of the LAN.
- It can route to other networks.
37
What happens when a device has no default gateway or a bad gateway?
If a device has no default gateway or a bad default gateway, its traffic will not be able to leave the LAN.
38
What is Router Packet Forwarding Decision?
It's the process of determining the next hop or path for a data packet to be sent towards its destination based on the packet's destination IP address
39
What happens when a packet arrives on a router interface?
- Looks at the destination IP address
- Then, it checks the routing table that lists the network addresses and tells it which way to send the data to those addresses
- Next, the router tries to find the most specific address in the table that matches the receiver's address on the packet. It prefers more detailed instructions.
- Lastly, Following the instructions in its routing table, the router sends the packet out through the correct interface to get it closer to its final destination.
40
What is static routing?
Static routing is a manual, non-adaptive routing method where network administrators configure specific routes in a router's routing table
41
How is the static route confugured?
It Must be configured manually
42
Who adjusts the static routing?
The administrator adjusts manually the static route when there is a change in the topology
43
For what type of networks static routing is good for?
It's Good for small non-redundant
networks
44
Where are static routes often used?
They are Often used in conjunction with a dynamic routing protocol for configuring a default route
45
What is dynamic routing?
Dynamic routing is a networking technique where routers automatically update and share information about the best paths for data to travel across a network
46
What does the dynamic routes automatically do?
- Discover remote networks
- Maintain up-to-date info
- Choose the best path to the destination
- Find new best paths when there is a topology change
47
Can dynamic routing also share static default routes with other routers?
Yes.
48
What are the two primary addresses assigned to a device on an Ethernet LAN?
Layer 2 physical address (the MAC address) and Layer 3 logical address (the IP address)
49
What is the MAC address used for?
They are used for NIC to NIC communications on the same Ethernet network
50
What is the IP address used for?
They are Used to send the packet from the source device to the destination device
51
Can layer 2 addresses be used to deliver frames from one NIC to another on a different network?
No, Layer 2 addresses are used to deliver frames from one NIC to another NIC on the same
network
52
What happens when a destination IP address is on the same network?
The destination MAC address
will be that of the destination device.
53
What happens when the destination IP address is on a remote network?
The destination MAC address is
that of the default gateway
54
For what is ARP used for?
ARP is used by IPv4 to associate the IPv4 address of a device with the MAC address of the device NIC
55
What is ARP?
The Address Resolution Protocol is a layer 2 protocol used to map MAC addresses to IP addresses
56
What is ICMPv6 used for?
ICMPv6 is used by IPv6 to associate the IPv6 address of a device with the MAC address of the device NIC
57
What is ICMPv6?
The Internet Control Message Protocol version 6, is a protocol within the IPv6 network suite that provides error reporting and diagnostic functions
58
For what does a device use ARP for?
A device uses ARP to determine the
destination MAC address of a local
device when it knows its IPv4 address
59
What are the two basic functions that ARP provides?
- Resolving IPv4 addresses to MAC addresses
- Maintaining an ARP table of IPv4 to MAC address mappings
60
What are IPv6 Neighbor Discovery Messages?
They help devices on the same local network find each other, check if they're online, and automatically get ready to communicate.
61
What does the IPv6 Neighbor Discovery (ND) protocol provide?
- Address resolution
- Router discovery
- Redirection services
- ICMPv6 Neighbor Solicitation (NS) and Neighbor Advertisement (NA)
messages are used for device-to-device messaging such as address
resolution.
- ICMTPv6 Router Solicitation (RS) and Router Advertisement (RA) messages are used for messaging between devices and routers for router discovery.
- ICMPv6 redirect messages are used by routers for better next-hop selection.
62
What is an IPv4?
An IPv4 address is a 32-bit hierarchical address that is made up of a network portion
and a host portion
63
What must you look at when determining the network portion versus the host portion?
The 32-bit stream
64
What is a subnet mask used for?
A subnet mask is used to determine the network and host portions
65
What is the prefix length?
A prefix length is a less cumbersome method used to identify a subnet mask address. It's the number of bits set to 1 in the subnet mask.
66
How it the prefix length written?
It is written in “slash notation”
therefore, count the number of
bits in the subnet mask and
prepend it with a slash.
67
What are the 3 network types of an IP address?
- Network address
- Host addresses
- Broadcast address
68
What is VLSM?
Variable Length Subnet Mask is a networking technique that allows network administrators to divide an IP address space into subnets of different sizes, using different subnet masks for each subnet.
69
What should you do when using VLSM?
You have to always begin by satisfying the host requirements of the largest subnet and continue subnetting until the host requirements of the smallest subnet are satisfied.
70
Why is there a need for IPv6?
IPv4 address space is running out of addresses, and IPv6 is the successor with a much larger 128-bit address space.
71
What are some of the challenges with IPv4 that make IPv6 necessary?
Limited IPv4 address space, issues with NAT, and the growth of the Internet of Things (IoT).
72
Will IPv4 and IPv6 coexist?
Yes, IPv4 and IPv6 will coexist for several years during the transition.
73
How long are IPv6 addresses and what format are they written in?
IPv6 addresses are 128 bits in length and written in hexadecimal.
74
Are IPv6 addresses case-sensitive?
No, IPv6 addresses are not case-sensitive and can be written in either lowercase or uppercase.
75
What is the preferred format for writing an IPv6 address?
The preferred format is x:x:x:x:x:x:x:x, where each “x” consists of four hexadecimal values.
76
What is a hextet in the context of IPv6 addressing?
A hextet is the unofficial term for a segment of 16 bits, or four hexadecimal values.
77
What is Rule 1 for reducing the notation of IPv6 addresses?
Rule 1 is to omit leading zeros from each hextet. (Ex: 0a00 → a00, 00ab → ab, etc.)
78
What is Rule 2 for IPv6 address notation?
Rule 2 involves using a double colon (::) to replace any contiguous string of one or more 16-bit hextets consisting of all zeros
79
How many times can the double colon (::) be used in an IPv6 address?
The double colon (::) can only be used once in an address, otherwise it would lead to ambiguity. (Ex: 2001 :0db8:0000:1111:0000:0000:0000:0200 → 2001:db8:0:1111::200)
80
What are the 3 different categories of IPv6 addresses?
Unicast, multicast, and anycast
81
What does Unicast do?
Unicast uniquely identifies an interface on an IPv6-enabled device.
82
What does Multicast do?
Multicast is used to send a single IPv6 packet to multiple destinations.
83
What does Anycast do?
This is any IPv6 unicast address that can be assigned to multiple devices. A packet sent to an anycast address is routed to the nearest device having that address
84
What does the IPv6 prefix length represent?
It represents the network portion of an IPv6 address.
85
What is the range of IPv6 prefix lengths?
The prefix length can range from 0 to 128.
86
What is the recommended prefix length for LANs and most networks?
The recommended prefix length is /64.
87
What are the two main unicast IPv6 addresses?
Global Unicast Address (GUA) and Link-local Address (LLA)
88
What is GUA?
Global Unicast Address is similar to a public IPv4 address. These are globally unique, internet-routable addresses
89
What is LLA?
Link-local Addresses are Required for every IPv6-enabled device and used to communicate with other devices on the same local link. LLAs are not routable and are confined to a single link.
90
What are IPv6 Global Unicast Addresses (GUAs)?
They are globally unique and routable on the IPv6 internet.
91
What prefix do currently assigned GUAs begin with?
GUAs begin with the first three bits 001, which is written as 2000::/3.
92
What is the global routing prefix in a GUA?
It is the network portion of the address assigned by a provider (e.g., ISP) to a customer or site.
93
What is the purpose of an IPv6 Link-Local Address (LLA)?
To allow communication between IPv6-enabled devices on the same local link (subnet).
94
Can packets with a source or destination LLA be routed?
No, LLAs are only valid within the local link and cannot be routed.
95
Does every IPv6-enabled interface need a Link-Local Address?
Yes, every IPv6-enabled network interface must have an LLA.
96
What happens if a Link-Local Address is not manually configured?
The device will automatically generate one.
97
What is the address range for IPv6 Link-Local Addresses?
fe80::/10
98
What protocol is used to dynamically obtain IPv6 GUA addresses?
Internet Control Message Protocol version 6 (ICMPv6).
99
What is the purpose of a Router Solicitation (RS) message?
It is sent by host devices to discover IPv6 routers on the network.
100
What is the purpose of a Router Advertisement (RA) message?
It is sent by routers to inform hosts how to obtain an IPv6 Global Unicast Address (GUA).
101
What are the three methods an RA can specify for IPv6 address configuration?
SLAAC, SLAAC with stateless DHCPv6, and Stateful DHCPv6 (no SLAAC).
102
