Security Plus Part 2
DNS lookup-
dig command on Linux, you enter 'dig and website name like professor messer.com and it does a query (it shows the results of when it shows up). text based.
on Windows, its nslookup command.
2.3
authentication server- you put name and password and it gives access to central server
-not in personal home, since everyone can share the same password
- in an enterprise, where we need more security everyone has their own credentials
NTP server- network time protocol. all the computers need to reference the same time for accuracy.
load server/balancer: is a system (hardware or software) that distributes incoming network traffic across multiple servers.
it makes sure the site doesn't crash. it balances out the load amongst different servers, spreads the load.
2.4 DNS configuration
DHCP-automatically give IP addresses to different devices in a large network. started in 1997. prevents someone having to do it manually. (dynamic host configuration protocol)
2.4 vlans and vpns
virtual local area networks can be separate inside the same hardware. they prevent messages to be received by everyone, only those that are sharing the same lane.
vlan networks- multiple devices int he same broadcast domain, separated logically instead of physically
ex. a broadcast (message) goes to the red part and everyone in that network receives it, not the blue part and vice versa.
router- needed to communicate from one VLAN to another as needed
VPN- virtual private networks. used across a public network, it sends all the data encrypted.
VPN concentrator- can encrypt and decrupt within vlans.
concentrator can be configured into the firewall.
2.5 network devices
routers- routes traffic between IP subnets. connects networks and directs traffic. can be physical or virtual and needed to communicate between VLANS.
A switch is a network device that connects multiple devices within the same network and intelligently sends data only to the device it’s meant for.
What a switch does
When devices (PCs, printers, servers) are connected to a switch:
- The switch learns each device’s MAC address
- When data comes in, it forwards it only to the correct port, not everyone
L3 switch- has routing and switch capabilities, it does both.
access point- extends the wired network into the wireless network. looks at the MAC address to decide whethere or not to forward.
RJ45 connector- is the standard wired networking connector. it connects devices to a VLAN.
it sends data between computers, switches and routers.
network closet- central hub or control room where all the cable wires lead there and the connections are managed there.
firewall- filters traffic. can do so by port number or the application (online or remote access). now some routers have firewalls installed into them.
NIC_ Network Interface Card- we can use it to connect to the network without a Ethernet cable. its a hardware component (looks like we can insert it into the computer motherboard). also can receive data from the network. The NIC gives a specific MAC address
2.6 ipv4 and ipv6
IPV4 (Internet protocol version 4)) gives every device an IP address. made up 32 bit numbers. uses dotted decimals (172.14.254.1) most widely used IP system.
IPV6-newer one, has more addresseses.
NAT- solution to the finite IP addresses problems. 4.29 billion combinations available of the format of Ip addresses. and 20 billion devices available. NAT stands for Network address translation and what it does is that it creates private and public addresses.
-private IP addresses are not Internet routable. NAT can translate and use a ipv4 address to communicate to the Internet, while the private addresses inside the private network can communicate with each other and it can be thousands of them. only one address is needed when communicating to the internet?
IPV6 addresses are 128 bits, (instead of 8 like IPV4).
example of IPV6 fe80:0000:00005d18:cffd:8fd5. since they are so long, we rely on DNS to name them.
Static IP adressing- where we want the IP address to stay the same, not rely on DHCP. we can set it up manually on the device. another option, is to configure a specific IP address on the DHCP and reserve one, and it would load up everytime the device signs on.
turning dynamic into static- disable DHCP on the device, configure manually OR better is to do a Ip reservation in the DHCP server. (associate a MAC address to an IP address)
2.7 Internet connections
1) satellatite connections- communicate from earth to a satellite, then back to earth. when a storm comes through, the connection is not good. we call this rain fade.
2) fiber internet connection- travels using light frequencies between cables (wow!). most efficient way to transfer data. better than copper wires, but more expensive and also more expensive repair. longer distances to transfer than copper.
3) cable connection- we can transmit internet data over cable connection.
broadband- allows us to transmit different frequencies over the same copper wire.
4)DSL connection- usually for voice (phone service) but can also transfer data. you have to be within 1000 feet of it.
5) WISP- wireless internet service provider. looks like a green box on a electric wooden line. we need an antenna outside to connect to it. good for remote areas where other options are not available.
2.7 LAN- group of networks that are close to our location. (can be a floor in our building or close buildings)
WAN- wide area network- connects for a city or across the world.
PAN- personal area network. speakers to phone, Bluetooth or headphones like apple that are connected to the phone. uses NFC (near field communication)
2.8 network tools- (skipped this part)
3.1 display types
1) LCD- liquid crystal display. light behind crystal, very lightweight and cheap
MAN- metropolitan area network connects over a city. larger than LAN, smaller than WAN
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