Cisco^® CCENT Exam Cram Notes : Memory Details Of A Typical Cisco Routers

2. Cisco IOS

1.3 Memory Details of a Typical Cisco Router

1.3.1 DRAM

This memory is analogous to the memory in PCs. DRAM is a fast memory and loses its contents when the system is restarted (power cycled).

The DRAM has Main Processor Memory and Shared Input/Output (I/O) memory.

Main Processor Memory is used to hold routing tables, fast switching cache, running configurations, and so on. It can take unused shared I/O memory, if needed.

Shared I/O memory is used for temporary storage of packets in system buffers.

1.3.2 Flash

Flash memory is typically located on a processor board SIMM card. Flash is a permanent storage for the Cisco IOS software image, backup configurations, and any other files. Cisco IOS software is run from the flash memory, these image files are defined as re-locatable, because the Cisco IOS software image can be executed from different locations in the Flash.

1.3.3 NVRAM

NVRAM is a Non-Volatile RAM used as permanent storage and this memory is re-writeable. NVRAM is used to store the startup configuration. This is the configuration file that IOS reads after the router OS is loaded and running. It is a fast non volatile memory and does not lose contents when the router is switched off.

1.3.4 BOOT ROM

This refers to erasable programmable read-only memory (EPROM) and is used to permanently store the startup diagnostic code (ROM Monitor), and RxBoot. Boot ROM size is 2 MB. This type of memory consists of one or more memory chips on a router's processor board. This code runs when the router starts.

• 1. OSI and DoD Models
  • 1.1. OSI Models and its function
  • 1.2. DOD Models and its function
  • 1.3. TCP and UDP
  • 1.4. TCP and UDP Frames
• 2. Network topologies and Flow control
  • 2.1 Different Types of N/w Topologies
  • 2.2 CSMA/CD
• 3. Wireless LANs (SSIDs, WLC, etc.)
• 4. IPv4 Addressing
  • 4.1. Subnetting (IP4)
  • 4.2 VLSM
  • 4.3 Examples on subnetting
• 5. IPv6 addressing
• 6. Wide Area Networks (WANs)
  • 6.1. DTE and DCE
  • 6.2 Different cable types
  • 6.3 Interface specifications
• II. Cisco IOS
  • 1. Cisco Router Architecture
    • 1.1 Block Diagram
    • 1.2 Architectural Components of a Router
    • 1.3 Memory Details of a Typical Cisco Router
  • 2. Cisco Router (25xx series) and its interfaces
    • 2.1 Interfaces Explained
    • 2.2 Console Port Configuration
  • 3. Router modes of operation
  • 4. Frequently used copy commands
  • 5. Different types of router passwords
• III. Routing Fundamentals
  • 1. Routed and Routing Protocol
  • 2. Routing protocol types
  • 3. CDP and LLDP
  • 4. Static and Default route
  • 5. Floating static route
  • 6. IP routing and PPP
  • 7. RIP and RIPv2
• IV. Switching Fundamentals
  • 1. Introduction to Cisco Switches
  • 2. VLANs and VTP
  • 3. VLAN Frame tagging
  • 4. Switching methods
  • 5. Switch configuration commands
  • 6. File systems available in Catalyst switches and their usage
  • 7. Switch ports and port security
• V. Infrastructure Services & Maintenance
  • 1. DNS
  • 2. DHCP
  • 3. NAT
  • 4. Access-lists
  • 5. Diagnostic commands
  • 6. Show commands and other related commands
• VI. Appendix
  • 1. IEEE standards