Summary

a networking refresher of topics

  • IP Addresses
  • OSI Model
  • Subnetting
  • MAC Addresses
  • TCP and UDP
  • Common Ports and Protocols

IP Addresses

  • At Layer 3 - routing

IPv4 versus IPv6

IPv4 uses 2^23 addresses. WE are out of IPv4 IP addresses! 😱

NAT

  • NAT makes IP addresses appear as if multiple requests are all coming out from a single source. There are local addresses to the machine, or private IP addresses.

  • Local Network 10.10.x.x
  • Private Network 192.168.x.x

MAC Addresses (Media Access Control)

  • At Layer 2 - Physical Interface (Network Interface)

The first three sets of characters in your MAC address can tell a user what the manufacter of that component is in your machine. You can take those first three sets of characters and paste them into https://maclookup.app/search

TCP and UDP

User Datagram protocol (UDP)

UDP is great for connection which don’t require guarantee that the client received a package.

Transmission Connection Protocol (TCP)

TCP is guaranteed that a connection is made to the client and requires that each party ackwnowledges that they received their piece of information.

SYN > SYN ACK > ACK

Common Ports and Protocols

  • TCP
    • FTP (21)
    • SSH (22)
    • Telnet (23)
    • SMTP (25)
    • DNS (53)
    • HTTP (80) / HTTPS (443)
    • POP3 (110)
    • SMB (139 + 445)
    • IMAP 143
  • UDP
    • DNS (53)
    • DHCP (67, 68)
    • TFTP (69)
    • SNMP (161)

OSI Model

  1. Physical - Cables and CAT-E
  2. Data Link - Switches, MAC Address
  3. Network - IP Addresses and Routing
  4. Transporation - TCP/UDP
  5. Session - session management
  6. Presentation - WMV, JPG, MOV
  7. Application - HTTP, SMTP, IMAP

Resources

  • https://en.wikipedia.org/wiki/OSI_model

Subnetting

  • Submetting using something like a spreadsheet can be really helful
  • The number of hosts that you can have on your private network depends on your subnet mask
  • The more “bits” turned off the larger pool of hosts.

Bit Table for subnetting

Subnet Bits
255.255.255.0 1 1 1 0

Resources