NOTES FOR COMPTIA

 LINK LOCAL ADDRESS   always starts w/ " fe80 " followed by 3 clusters of 4 zeros Ex. = fe80:0000:0000:0000 [last half is auto generated] . GLOBAL UNICAST ADDRESS   aka IPv6   is   automatically generated by your PC + ROUTER Use COMMAND SCREEN: " >ipconfig " to see your IPv6 address SUBNET MASK does not really apply to IPv6 IPv6 uses a prefix length stuck at "/64" in place of SUBNET MASK . . . . . . PORT NUMBERS * Web browser is a web client . They use WEB SERVERS   (like "apache" or "i.i.s.") DNS = Domain name system: like a speed-dialer that zips you to a site's WEB SERVER After IP address & DNS - a PORT NUMBER gets you to the right application . PORT# example: 0-65535  . *when browsing internet there are 2 port #s*  The "SOURCE" port  + "DESTINATION" PORT numbers (like a train) Webpage DATA < PORT 1 (source) < PORT 2 # (destination) < outgoing IP < intercepting IP . Like ...

DHCP = DYNAMIC HOST CONFIGURATION PROTOCOL DHCP is a type of server that automatically gives you a new IP ADDRESS  each time. No longer static IP. VPN disguises all IP ADDRESSES! . . . . . OPEN NETWORK & SHARING - CHANGE ADAPTOR SETTINGS  - PROPERTIES - INTERNET PROTOCOL TCP/IPv? You can toggle between DHCP "obtain IP automatically" or manually enter one. COMMAND SCREEN will reveal even more (like DHCP server address):   >ipconfig /all . . . . . If DHCP server goes down?   your PC has "APIPA" to fallback on to assign new IP addy.   **But this is only for office intranet** . . . OPEN NETWORK & SHARING - CHANGE ADAPTOR SETTINGS  - PROPERTIES - INTERNET PROTOCOL TCP/IPv? - then go to "alternate configuration" tab . to toggle . . . . Apipa ALWAYS gives out addresses like this: 169.254.?.? *CLASS B address . . . . Sometimes you can't get on internet & **it's because your settings are stuck on APIPA** COMMAND SCREEN will reveal if y...

IPv4 ADDRESSes built the internet. But they ran out of combos in late 90s   NAT "network address translation" fixed this You used to have to be manually assigned a network ID via your internet provider Downside of this was your network ID was public to hackers = therefore FIREWALL was born . If someone got past your " Firewall "  all of the PCs on your WAN & LAN were vulnerable **NAT fixed this too** NAT router/gateway will now give private IP addresses to all PCs on a LAN . Your private IP ADDRESS goes through NAT gateway  & the gateway camouflages your address as its own LAN address (Kinda slows things down unfortunately) . .

  Class C   IP ADDRESS =   210.11.12. ? your first 3 clusters of IP ADDRESS are set in stone. 4th cluster is unique Class B  IP ADDRESS  =  210.11. ? . ? First 2 clusters of IP ADDRESS set in stone. 3rd & 4th cluster unique Class A   IP ADDRESS  =  210. ? . ? . ? First cluster of IP ADDRESS set in stone. 2nd, 3rd, & 4th cluster unique Class C  IP ADDRESS =  only 254 hosts Class B  IP ADDRESS =  65,534 hosts Class A  IP ADDRESS =  Millions of hosts . . . . . Class A IP ADDRESS =   126. ? . ? . ? in class A the first cluster could only start with a 1 or 126! Class B IP ADDRESS =   128.11. ? . ? First cluster could be anywhere between 128-191 Class C IP ADDRESS =  223.11.12. ? First cluster could be only be between 192-223 . . . . . **SPECIAL IP ADDRESSES** Class D-"multicast" IP ADDRESS = 224. ? . ? . ? First cluster could only start w/224 (these were for live presentations) spooky Cla...

  LOGICAL ADDRESS aka "IP ADRESS" looks like 192.168.5.10 . . . . TIER 1 early internet Internet began via telephones at military base LANs during Cold War . . . . . . . TCP/IPs  TCP/IPs go from 0 to 254                                       ... = never beyond 254 and always w/3 dots mixed in (192.168.5.10) **IP addy never ends with a lone ZERO or 255** . . . . . . . IP ADDRESS: 192.168.5.10 IP ADDRESS the 4 cluster "octet" numbering system  was invented by ARPA to identify each military LAN . . . . . . . IP ADDRESS:  192.168.5.10 . Your 4 cluster "octet" : A) Identifies what LAN you're part of B) shows your unique host ID . . Class C IP ADDRESS =   210.11.12. ? your first 3 clusters of IP ADDRESS are set in stone. 4th cluster is unique Class B IP ADDRESS =  210.11. ? . ? First 2 clusters of IP ADDRESS set in stone. 3rd & 4th cluster unique Class ...