Module2 Flashcards
ARP
Address Resolution Protocol. Associates a MAC address with an IP address in an ARP table, so that devices can communicate in a LAN
IP Address
Internet Protocol Address is the address of a device connected to a network
It is made up out of 4 octets.
Each octet can represent numbers between 0 and 255
How are IP addresses assigned
IP addresses belong to the network and not to the devices attached to the network. They are assigned to devices by the LAN using DHCP, which is why the same device can have different IP addresses on different networks.
DHCP
Dynamic host configuration protocol. A protocol used by LANs to assign dynamic IP addresses.
Static IP vs Dynamic IP
static IP addresses are reserved for servers and networks devices, while dynamic IP addresses are reserved for clients.
Static IP needs to be configured manually, while dynamic IP is assigned though DHCP
What are data packets called at the Network layer?
IP datagram
IP datagram header parts
- Version (4 bits) - ip4/ip6
- Header length (4 bit)
- service type (8bits) - quality of service
- Total length (16bit)
5.Identification (16bit) - Flags (3) - indicates whether datagram is fragmented
- fragmentation offset (12)
8 TTL - How many hops a datagram can traverse before data is thrown away - Protocol field - TCP/UDP
- Header Checksum -
- Source IP address (32 bit)
- Destination IP address (32bit)
- IP options field
- Padding - A series of 0s used to ensure the header is the correct total size
What is the maximum size of a datagram, and what happens when this size is exceeded?
The maximum size is the largest number you can represent with a 16 bit number which is 65,535.
If the total amount of data is larger than what can be fitted into a single datagram, the ip layer will split this data up into many individual packets, through a process called fragmentation
Through the process of encapsulation, what headers is the message wrapped in?
- Ethernet Header
- IP header
- TCP/UPD header
- Message
- Ethernet Footer
Two sections of an IP address
- network ID - first octet
- Host ID - second, third, and fourth octet
Address class system
A way of defining how the global IP address space is split up
Three types
1. Class A - Network = 1, Host = 3 - 0xxx - 0 to 127
2. Class B - Network = 2, Host = 2 - 10xx - 128 - 191
3. Class C - Network = 3, Host = 1 - 110x - 192 - 223
- Class D - 1110 - 224 to 239 - used for multicasting
- Class E - 1111 - 240 to 255 - used for testing
ARP
Address Resolution Protocol. Used to discover the hardware address of a node with a certain IP address
ARP poisoning
AKA man in the middle attack is a Technique used by hackers to trick a LAN device into thinking that the hacker’s device is the default gateway, so that all data is sent to the hacker’s device instead of the default gateway.
ARP table
ARP table AKA ARP Cache is a list of IP addresses and the MAC addresses associated with them.
ARP table entries generally expire after a short amount of time to ensure changes in the network are accounted for.
Subnetting
The process of taking a large network and splitting it up into many individual and smaller subnetworks, or subnets
Subnetting is done by changing the subnet mask.
Gateway router
Entry and exit points for specific networks or parts of networks
Subnet ID
A 32 bit number that Identifies a subnet. Usually the first octet of the host ID
Subnet Mask
32-bit numbers that are normally written out as four octets in decimal. It is used to identify the subnet ID and the host ID in an IP address