Lesson 5: Explaining IPv4 Addressing Flashcards
What does the version field in an IP header indicate?
The version of internet protocol being used
What does the length field in an IP header indicate?
The size of the header and the total packet size including the payload (65,535 bytes max)
What does the protocol field in an IP header indicate?
Identifies the protocol working over IP at the transport layer (layer 4) so the receiving host knows how to process it
What are the possible protocols that can be defined in the protocol field?
TCP, UDP, ICMP, GRE, EIGRP, or OSPF
What protocols run directly on IP instead of at the transport layer?
ICMP, IGMP, GRE, ESP, and EIGRP
What is a network mask (netmask)?
The number of bits used to distinguish between the network ID and a host ID of an IP address and both are 32 bits
How does one determine the network ID of an IP address?
By ANDing the network mast to the IP address
Define the ANDing process
- Convert the network mask and IP address to binary and and the binary numbers together, like an addition problem, two 1s equal 1, any other combination equals 0, the result is the network ID
What is a network prefix or slash notation?
The abbreviated version of the decimal network mask added to the end of the network ID to describe mask
What is the decimal notation of an 8-bit mask
255.0.0.0
What is the decimal notation of a 16-bit mask
255.255.0.0
What is said to happen when deceasing the bits in the network mask?
Decreasing the bits in the network mask allows for a larger number of hosts in each network because it allows for more host IDs but decreases the number of network IDs in the total network space
What is said to happen when increasing the bits in the network mask?
Increasing the bits in the network mask allows for a smaller number of networks allowed in the overall network because it allocates more bits to the host IDs which increases the number of host IDs possible in each network
What is subnet addressing?
Division of a single IP network into two or more smaller broadcast domains by using longer netmasks within boundaries of a network
What are the hierarchical levels of subnet addressing?
- Network ID
- Subnet ID
- Host ID
How are logical subnets created?
Bits from the host ID are allocated to the subnetwork address, meaning that the subnet ID lies within an octet boundary
What does adding a bit to the mask do to the number of host addresses?
It halves the number of available host addresses and doubles the number of possible networks or subnets
What is the term for forwarding packets at layer 3/network layer?
Routing
Define a default gateway
A host/node IP configuration parameter that identifies the address of a router on the local subnet that the host/node can use to communicate with other networks.
What is the function of a router?
Based on the rules of the routing table, as well as source/destination IP and netmask, the router determines where to forward packets, if no suitable path it will drop the packet and inform that it could not be delivered
Define dynamic routing
Allows routers to share information about known networks and possible paths to them
How do hosts in the same ethernet network identify each other?
When host are within the same broadcast domain or subnet, local address resolution takes place using ARP requests and ARP replies
Define the ARP (Address Resolution Protocol) process
- The sending host will check ARP cache, if it’s empty it will send ARP broadcast request thru network
- Only the host with the destination IP address will respond with its MAC address
- The sending host will cache the mapping and encapsulates the IP packet in a frame with the destination MAC address
How does ARP function if the destination address is on a remote network?
The local host determines the MAC address of the default gateway and forwards the packet to the router
What is a broadcast address?
The broadcast address of IP is one where the host bits are all set to 1; at the MAC layer it is the address ff:ff:ff:ff:ff:ff.
What is multicasting?
Allows a host to send content to other hosts in a special group intended to receive that content
What is a multicast address?
A special range of IPs configured for multicast packets
What is IGMP?
Internet Group Management Protocol is a layer 3 protocol used to configure multicasting group memberships and multicast addresses
Define Anycast addressing
A group of hosts that share the same IP address, typically used for load balancing/failover between hosts.
What is the function of a VLAN?
To create a logically separate network on a switch, which creates separate broadcast domains to decrease broadcast traffic,; devices in these separate domains will need a router to communicate
What are the different classes of classful addressing?
- Class A
- Class B
- Class C
Define classful addressing
It allocates the network ID based on the first octet of the IP address
Define Class A
First octet is 1-126; supports a large number of hosts over 16 million but only 126 network addresses, with a netmask of 255.0.0.0 or (/8)
Define Class B
First octet from 128-191; Has 16,000 networks each up to 65,000 hosts; Netmask of 255.255.0.0 or (/16)
Define Class C
First octet form 182-223; Has 2 million networks with up to 254 hosts each; Netmask of 255.255.255.0 or (/24)
What governing body allocates public IP addresses?
IANA - Internet assigned number authority
What are the private IP ranges?
Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255
What does a windows device do if it can’t contact a DHCP server?
To be able to still communicate with other devices, it will assign itself it selects an APIPA (Automatic Private IP Addressing) address
What is the APIPA (Automatic Private IP Addressing) range?
169.254.1.1 to 169.254.254.254; 169.254.0.0/16
What is APIPA (Automatic Private IP Addressing) classified as?
Classified as “link local addressing” in RFC 3927, similar to bonjour for MacOS and Avahi for Linux
What class of addressing does multicast use?
Class D; Addresses 244.0.0.0 thru 239.255.255.255
What is the use class E addressing?
Experimental use and testing