117 Final Study Guide Flashcards
What are the four basic operations of the network layer?
- Addressing end devices
- Encapsulation
- Routing
- De-Encapsulation
What does the network layer provide?
The network layer provides services to allow end devices to exchange data.
What are the two principle network layer communication protocols?
IPv4 and IPv6
What is IP Encapsulation?
IP encapuslation encapsulates the transport layer segment using either an IPv4 or an IPv6 packet. It does not impact the Layer 4 segment.
The IP packet will be examined by all layer 3 devices as it traverses the network.
Does IP addressing change during travel?
No, IP addressing stays the same from source to destination.
What are the characteristics of IP?
IP is meant to have low overhead and may be described as:
Connectionless
Best Effort
Media Independent
What are the 3 types of routes inside of a routing table?
Directly connected (Routes automatically added to the router, provided it is active and has addressing)
Remote ( Routes the router does not have a direct connection to, but may learn either manually or dynamically)
Direct route (This forwards all traffic to a specific direction where there is not a match in the routing table)
What are the characteristics of static routing?
Static routes must be configured manually
Static routes must be adjusted manually if there is a change in topology
Good for small, non-redundant networks
Often used in conjunction with dynamic routing for configuring a default route.
What are the characteristics of dynamic routing?
Dynamic routes automatically:
Discover remote networks
Update information
Choose the best path to a destination
Find new best paths when there is a change in topology.
Can dynamic routing share static default routes?
Yes, dynamic routing can share static default routes with other connnected routers.
What command is used to access the IP routing table?
show ip route for IPv4
show ipv6 route for IPv6
What are the route sources listed in the routing table?
- Directly Connected Routes:
- L - Directly conected local interface IP address
- C - Directly Connected Network
- Default Routes
- S - Manually configured static route
- R - Rip route
- Remote Routes
- O - OSPF
- D - EIGRP
What is ARP?
ARP (Address Resolution Protocol) is used to determine the destination MAC address of a local device when it knows its IPv4 address already.
Name the 2 basic functions of ARP
ARP Resolves IPv4 addresses to a MAC address
ARP maintains an ARP tables of IPv4 to MAC address mappings.
How does ARP function?
To send a frame a device will search its ARP table for a destination IPv4 address and a corresponding MAC address.
ARP sends out a broadcast (255.255.255.255) to all devices on the LAN it’s connected to. Only the device with the correct IP address responds with its MAC, and an entry is made in the ARP table.
Describe 4 ways ARP functions in a router.
- If the packets destination IPv4 address is on the same network, the device will search the ARP table for the destination IPv4 address
- If the destination IPv4 address is on a different network, the device will search the ARP table for the IPv4 address of the default gateway
- If the device locates the IPv4 address, its corresponding MAC address is used as the destination MAC address of the frame
- If no ARP entry is found, the device will send out an ARP request.
Name the commands used to show the ARP table.
show ip arp is used on Cisco routers
arp - a is used on Windows 10 PCs
What does IPv6 Neghibor Discovery provide?
IPv6 ND provides:
- Address resolution
- Router Discovery
- Redirection Services
- ICMPv6 Neghibor Solicitation (NS)
- ICMTPv6 Router Solicitation and Router Advertisement
- ICMPv6 redirect messages used by routers for better next-hop selection
What is Neghibor Solicitation and Neghibor Advertisement used for?
NS and NA are used for device to device messaging such as address resolution.
What is Router Solicitation and Router Adverrtisement used for?
RS and RA are used for communication between devices and routers for router discovery.
Define an IPv4 Address.
An IPv4 address is a 32-bit hierarchial address that is made up of a network and a host portion.
How do you determine the network and host portion of an IPv4 address?
A subnet mask is used to determine the network and host portions.
How is a subnet mask used?
To identify the network and host portions of an address, the subnet mask is compared to the IPv4 address bit for bit, from left to right.
What is the name of the process used to identify network and host portions of an address?
The process is called ANDing.
Define prefix length.
A prefix length is a truncated method to identify a subnet mask address.
The prefix length is the number of 1 bits in a subnet mask.
How do you write prefix length in slash notation?
Count the number of bits in the subnet mask and prepend it with a slash.
Example:
- 255.255.255.0
- 11111111.11111111.11111111.00000000
- 24 ones, prefix length is /24
Describe the process of ANDing.
ANDing is a logical Boolean operation.
It is the comparison between two bits where only 1 AND 1 produce 1 and any other combination results in a 0.
1 = True and 0 = False.
What are the 3 types of IP addresses inside of each network?
Network Address (First in the range)
Host addresses (2nd address to 2nd last address in the range)
Broadcast address (Final Address in the range)
Example:
192.168.1.0/30
- 192.168.1.0 - network address
- 192.168.1.1 and 2 - host addresses
- 192.168.1.3 broadcast address.
What are Unicast transmissions?
Unicast transmission is sending a packet to a SINGLE destination IP address.
What are Broadcast transmissions?
Broadcast transmission is sending a packet to ALL destination IP addresses on a network.
What are Multicast Transmissions?
Multicast transmissions send a packet to a SPECIFIED multicast address group.
What are public IPv4 addresses?
Public IPv4 addresses (as defined in RFC 1918) are globally routed between ISP routers.
What are Private IPv4 addresses?
Private IPv4 addresses are common blocks of addresses used by most organizations to assign IPv4 addresses to internal hosts.
Private IPv4 addresses are not Unique and can be used internally within any network, however they are not privately routable.
Name the 3 ranges of IPv4 Private Addresses.
- 0.0.0/8 (10.0.0.0 - 10.255.255.255)
- 16.0.0/12 (172.16.0.0 - 172.31.255.255)
- 168.0.0 /16 (192.168.0.0 - 192.168.255.255)
What are Loopback Addresses?
Loopback addresses (127.0.0.0 / 8 or any address starting in 127 up to 127.255.255.254) are used on a host to test if TCP/IP is operational.
What are Link-Local addresses.
Link local addresses are commonly known as the Automatic Private IP Addressing (APIPA) addresses. Also known as self assigned addresses. They are used by Windows DHCP clients to self-configre when DHCP servers are unavailable.
What range are Class A addresses allocated?
0.0.0.0/8 to 127.0.0.0/8
What range are Class B addresses allocated?
128.0.0.0/16 to 191.255.0.0/16
What range are Class C addresses allocated?
192.0.0.0/24 to 223.255.255.0/24
What range are class D addresses allocated?
224.0.0.0 to 239.0.0.0
What range are Class E addresses assigned to?
240.0.0.0 - 255.255.255.255
Why is Classful addressing no longer used?
Classful addressing was wasteful and has been replaced with classless addressing which ignores the rules of classes.
How does prefix length affect the number of hosts per subnet?
The longer the prefix length, the less hosts per subnet.
Why do we segment networks?
Large broadcast domains have the ability to generate excessive broadcasts which negatively affect the network.