I have been using Hamachi since first hearing about it on Security Now, over 10 years ago. Hamachi is a hosted virtual private network solution that can create links with devices that are behind NAT firewalls. Hamachi is able to do so by using server-assisted NAT traversal. I mostly use it to access virtual machines from outside of my house. Continue reading
IPv4 addresses are divided into five classes. Each IP address class has a different maximum number of IPs that exist within it.
|Class||First Octet Range||Default Subnet Mask||Maximum Number of Hosts Per Network|
|A||1-127||255.0.0.0||16,777,214 Hosts (2^24-2)|
|B||128-191||255.255.0.0||65,534 Hosts (2^16-2)|
|C||192-223||255.255.255.0||254 Hosts (2^8-2)|
Class A IPs start with 1-127. Keep in mind, though, that 127 is reserved for localhost. The remaining three octets are used for the host id. Class B IPs start with 128-191 and use the first and second octets for the network id. Class C begins with 192-223 and use the first three octets for the network id. Class D and class E are not generally used for setting up networks. Class D is Multicast and class E is experimental.
This week’s phone app is the Network+ Vocabulary App. I have been taking a Network+ class at the Milwaukee Area Technical College and I figured that writing a study guide for the test, would both net me another app and help me study.
For note, this covers the vocabulary for exam N10-005.
The OSI (Open Systems Interconnection) model, is a conceptual model of computer-to-computer communications, over a network. It was defined was defined in ISO/IEC 7498-1, by the International Organization for Standardization (ISO) in 1984. The model is not meant to specify exactly what processes occur. Instead, it describes them.
The OSI model, has seven layers: (1) Physical, (2) Data Link, (3) Network, (4) Transport, (5) Session, (6) Presentation, and (7) Application. As data flows from the source to the destination, it flows from the application layer (layer 7) to the physical layer (layer 1), across to the other computer, and back up from the physical layer (layer 1) to the application layer (layer 7).