2.

Communication Entity
- Source
- Medium
- Destination
Protocols
- message encoding
- message formatting and encapsulation
- message size
- message timing
- message delivery
Model
- OSI
- TCP/IP
  - Application
  - Transport
  - Internet
  - Network Access
Communication Process
- Segmentation
- Multiplexing
- Encapsulation
- De-encapsulation
Protocol data unit (PDU)
- Data - Application layer
- Segment - Transport layer
- Packet - Internet layer
- Frame - Network access layer
- Bits - Physical layer
Address
- Data Link
  - Ethernet (MAC)
- Network
  - IP (IPv4, IPv6)
Internetwork Operating System
- Store in Flash Memory
- Load into Memory
Command-line Interface (CLI)
- Access Method
  - Out of Band
    Console
    AUX
  - In Band
    Telnet
    SSH
- Terminal Emulation Program
  - Putty
  - Teraterm
- Access Mode
  - User (EXEC) mode
  - Privileged (EXEC) mode
  - Global configuration mode
  - Specific mode (interface/line configuration)

Hostnames allow devices to be identified by network administrators over a network or the Internet. Passwords are the primary defense against unauthorized access to network devices.

Enable password - Limits access to the privileged EXEC mode

Enable secret - Encrypted, limits access to the privileged EXEC mode

Console password - Limits device access using the console connection

VTY password - Limits device access over Telnet