CCDA 640-864 Summary Notes – Chapter 4 – Day 8

Exam Topic 4: Virtualization Overview

Virtualization technologies abstract logical elements from hardware (applications or operating systems) or networks (LANs and SANs) and run them in a virtual state

  • Allow a physical device to share its resources by acting as multiple versions of itself
  • Allow multiple physical devices to logically appear as one

Benefits of virtualization

  • improves network efficiency
  • provides enhanced flexibility – management, reassignment, resources
  • reduces operational expenses and increased uptime
  • Reduced power and space
  • Traffic isolation – separation of user groups
  • Per-departmental security policies
  • Better use of computing resources

Driving forces for virtualization adoption

  • Need to reduce power costs
  • Consolidation of assets – reduce number of devices
  • Logically separate user groups and traffic
  • Eliminate underutilized hardware

Virtualization types

  • Network Virtualization – logical isolation of network segments that share the same physicalinfrastracture
  • Device Virtualization – single physical device acts as many copies of itself or multiple physical devices to act as one logical unit
    • Server virtualization: Virtual machines (VM)
    • Cisco Application Control Engine (ACE) context
    • Virtual Switching System (VSS)
    • Cisco Adaptive Security Appliance (ASA) firewall context
    • Virtual device contexts (VDC)

Exam Topic 5: Virtualization Technologies

Virtualization – building abstracting logical entities from pooled physical resources

  • Virtual Machines
  • Virtual Switching Systems (VSS) – 2 6500 switches act as one logical virtual switch
    • Network Virtualization technology
    • Increased efficiencies
    • Ups bandwidth up to 1.4 Tb/s
    • Limited to 2 physical chassis connected together
    • Similar to Stackwise technology (Cisco 3750)
  • Virtual Switches
  • Virtual Storage Area Networks (VSAN)
  • Virtual Private Networks (VPN)
  • Virtual Routing and Forwarding (VRF)
    • Routing Virtualization technology
    • Creates multiple routing tables on the same physical router
    • Especially used in MPLS VPN environments – allows multiple networks to coexist in the same MPLS network
    • Routing information is in the VRF and is visible to only to routers participating in the same VRF
    • Duplicate IP addressing can be used as routing tables are separated
  • Virtual Local Area Networks (VLAN)
  • Virtual Port Channels (vPC)
    • Combines 2 Cisco Nexus 7000 or 5000 switches with 10GE
    • The switches act as one logical switch for port channeling
    • Enables the spanning-tree topology to appear loop-free although multiple redundant paths are present in the physical topology
  • Virtual Device Contexts (VDC)
    • Enables a single physical device to host multiple virtual network devices
    • Each context is independent – own policy, configuration, interfaces, management accounts 
    • Context operates similar to standalone devices
    • Supported in 
      • Nexus 7000 (VDC)
      • ASA
      • 6500 Firewall Services Module (FWSM)
      • Cisco Application Control Engine Appliance
      • 6500 Application Control Engine Module
      • IPS

Server Virtualization

Server virtualization –  software technique that abstracts server resources from the hardware.

  • The server virtualized hypersupervisor provides the foundation for the virtualized environment on the host
  • Hypersupervisor controls hardware and physical resources allocated to virtual machines running on the host
  • VMs are unaware of the physical hardware but can use CPU, memory, network infrastructure


Exam Topic 6: Network Virtualization Design Considerations

  • Access needs to be controlled
  • Path isolation eg using MPLS VPN to provide independent logical paths in a shared network
  • Secured edge – the right services should be available to the intended users or groups

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