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
What does a subnet mask of 255.255.255.0 mean?
That only the last octet of the IP is available for host ID’s, meaning it has 256 addresses available
CIDR
Classless Inter Domain Routing is a more flexible approach to describing blocks of IP addresses, by using subnet masks for demarcation
CIDR combines the network ID and the subnet mask into one
Example:
9.100.100.100/24
Demarcation point
A point that describes where one network or system ends and another one begins
IANA
Internet assigned numbers authority
What is 127.0.0.0?
IP addresses that start with 127 are loopback addresses, which are virtual addresses that live on your device, and are used for testing.
Example:
ping 127.0.0.1 can be used to check if a device is connected to the network.
also known as the “Home” address.
What are the differences between public and private Ip addresses?
A public IP address is an address that is globally unique across the entire internet. It is assigned by your Internet Service Provider (ISP) and allows your device to communicate with other devices across the internet. Public IP addresses are used for identifying devices on the broader internet. They can be accessed from any other internet-connected device. These addresses are visible to the public, meaning anyone on the internet can access a device with a public IP (if permissions and firewalls allow).
Example: 192.168.1.1 is a common private IP, while a public IP could be something like 203.0.113.5.
A private IP address is used within a private network (like your home or office network) and is assigned by the router. These addresses are reserved for internal use and cannot be accessed directly from the internet. Private IP addresses are used to identify devices within the same local network. They are used in LAN (Local Area Network) setups to allow devices to communicate with each other. Private IP addresses are not routable on the internet, meaning they are hidden and only usable within a network.
What are private Ip addresses classes?
A 10.0.0.0 - 10.255.255.255 (255.0.0.0)
B 172.16.0.0 - 172.31.255.255 (255.255.0.0)
C 192.168.0.0 - 192.168.255.255. (255.255.255.0)
NAT
Network Address Translation. Translates public to private Ip addresses and vice versa.
What is the size of an IPv4 address?
4 Octets = 4 Bytes = 32 bits
4 steps to subnetting
- Calculate the number of host bits needed
- Add host bits to subnet mask by hacking or saving
- Find the increment
- Create the networks.
VLSM
Variable length subnet Masking. Used to subnet networks of variable sizes
Router
A network device that forwards traffic depending on the destination address of that traffic
4 steps of basic routing
- Receive data package
- Examines destination IP
- Looks up IP destination network in routing table
- forward traffic to destination
Routing Table
Table used by router to determine which destination to forward data to.
Routing Protocols
Protocols the routers use to speak to each other in order to share what information they might have in order to determine the best path to get data to it’s destination
2 basic Routing Protocols
- Interior gateway protocols
- Exterior gateway protocols
2 Categories of interior gateway protocols
- Link state routing protocols
- distance-vector protocols.
exterior gateway protocols
EGPs are used to route traffic between different Autonomous Systems, such as across the public internet or between different companies’ networks. They are responsible for inter-AS routing.
interior gateway protocols
IGPs are used to route traffic within a single Autonomous System (AS), which is essentially a network or group of networks under a common administrative control (such as a company’s internal network).
Autonomous system
a collection of IP networks and routers under the control of a single organization that presents a unified routing policy to the internet. In simpler terms, an AS is a large network or a group of networks that is managed and operated by one or more network operators, typically for an Internet Service Provider (ISP), large enterprise, or academic institution.
Distance Vector Protocols
A vector is a list
Distance vector protocols determine the best path based on the distance (typically hop count) and direction (vector) to reach a destination. Routers using this protocol periodically share their routing tables with their neighbors.
Link State Protocol
Link-state protocols operate by having routers build a complete map of the network topology. Each router independently calculates the shortest path to every other router using algorithms like Dijkstra’s shortest path algorithm.
Edge Router
An edge router is a specialized router located at the boundary, or “edge,” of a network, connecting an internal network (such as a local area network, or LAN) to external networks, like the internet or other wide-area networks (WANs). It manages the flow of traffic between different networks and often serves as a gateway between an organization’s internal network and external networks.
ASN
An Autonomous System Number (ASN) is a globally unique identifier assigned to an Autonomous System (AS), which is a collection of IP networks under the control of a single organization, such as an Internet Service Provider (ISP) or large enterprise. The ASN is used to identify the AS in routing operations, particularly for Border Gateway Protocol (BGP), which is responsible for routing traffic between different ASes on the internet.
ASN vs IP
IP addresses direct traffic to the correct device within a network. ASNs are used by routers to route traffic between large networks or Autonomous Systems on the internet.
Non Routable Address Space
Non-routable address space refers to IP addresses that are reserved for internal use within private networks and cannot be routed on the public internet. Devices that use non-routable IP addresses can communicate with each other within the same local network, but they need a gateway (typically through Network Address Translation, or NAT) to access the internet.
Common Non-Routable IP Address Ranges (as defined by RFC 1918):
10.0.0.0 – 10.255.255.255 (Class A)
172.16.0.0 – 172.31.255.255 (Class B)
192.168.0.0 – 192.168.255.255 (Class C)
