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Virtualization Questions

March 16th, 2020 in ENCOR 350-401 Go to comments

Virtualization Quick Summary

A virtual machine (VM) is a software emulation of a physical server with an operating system. From an application’s point of view, the VM provides the look
and feel of a real physical server, including all its components, such as CPU, memory, and network interface cards (NICs).

The virtualization software that creates VMs and performs the hardware abstraction that allows multiple VMs to run concurrently is known as a hypervisor.

There are two types of hypervisors: type 1 and type 2 hypervisor.

In type 1 hypervisor (or native hypervisor), the hypervisor is installed directly on the physical server. Then instances of an operating system (OS) are installed on the hypervisor. Type 1 hypervisor has direct access to the hardware resources. Therefore they are more efficient than hosted architectures. Some examples of type 1 hypervisor are VMware vSphere/ESXi, Oracle VM Server, KVM and Microsoft Hyper-V.

In contrast to type 1 hypervisor, a type 2 hypervisor (or hosted hypervisor) runs on top of an operating system and not the physical hardware directly. A big advantage of Type 2 hypervisors is that management console software is not required. Examples of type 2 hypervisor are VMware Workstation (which can run on Windows, Mac and Linux) or Microsoft Virtual PC (only runs on Windows).

Type1_Type2_Hypervisors.jpg

Structure of virtualization in a hypervisor

Hypervisors provide virtual switch (vSwitch) that Virtual Machines (VMs) use to communicate with other VMs on the same host. The vSwitch may also be connected to the host’s physical NIC to allow VMs to get layer 2 access to the outside world.

Each VM is provided with a virtual NIC (vNIC) that is connected to the virtual switch. Multiple vNICs can connect to a single vSwitch, allowing VMs on a physical host to communicate with one another at layer 2 without having to go out to a physical switch.

 

Virtual_machine_structure.jpg

Although vSwitch does not run Spanning-tree protocol but vSwitch implements other loop prevention mechanisms. For example, a frame that enters from one VMNIC is not going to go out of the physical host from a different VMNIC card.

Benefits of Virtualizing

Server virtualization and the use of virtual machines is profoundly changing data center dynamics. Most organizations are struggling with the cost and complexity of hosting multiple physical servers in their data centers. The expansion of the data center, a result of both scale-out server architectures and traditional “one application, one server” sprawl, has created problems in housing, powering, and cooling large numbers of underutilized servers. In addition, IT organizations continue to deal with the traditional cost and operational challenges of matching server resources to organizational needs that seem fickle and ever changing.

Virtual machines can significantly mitigate many of these challenges by enabling multiple application and operating system environments to be hosted on a single physical server while maintaining complete isolation between the guest operating systems and their respective applications. Hence, server virtualization facilitates server consolidation by enabling organizations to exchange a number of underutilized servers for a single highly utilized server running multiple virtual machines.

By consolidating multiple physical servers, organizations can gain several benefits:
+ Underutilized servers can be retired or redeployed.
+ Rack space can be reclaimed.
+ Power and cooling loads can be reduced.
+ New virtual servers can be rapidly deployed.
+ CapEx (higher utilization means fewer servers need to be purchased) and OpEx (few servers means a simpler environment and lower maintenance costs) can be reduced.

Question 1

Explanation

There is nothing special with the configuration of Gi0/0 on R1. Only Gi0/0 interface on R2 is assigned to VRF VPN_A. The default VRF here is similar to the global routing table concept in Cisco IOS

Question 2

Explanation

Answer C and answer D are not correct as only route distinguisher (RD) identifies the customer routing table and “allows customers to be assigned overlapping addresses”.

Answer A is not correct as “When BGP is configured, route targets are transmitted as BGP extended communities”

Question 3

Explanation

In VRF-Lite, Route distinguisher (RD) identifies the customer routing table and allows customers to be assigned overlapping addresses. Therefore it can support multiple customers with overlapping addresses -> Answer E is correct.

VRFs are commonly used for MPLS deployments, when we use VRFs without MPLS then we call it VRF lite -> Answer C is not correct.

– VRF-lite does not support IGRP and ISIS. ( -> Answer B is not correct)
– The capability vrf-lite subcommand under router ospf should be used when configuring OSPF as the routing protocol between the PE and the CE.
– VRF-lite does not affect the packet switching rate. (-> Answer A is not correct)

Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/vrf.html#wp1045190

Question 4

Explanation

There are two types of hypervisors: type 1 and type 2 hypervisor.

In type 1 hypervisor (or native hypervisor), the hypervisor is installed directly on the physical server. Then instances of an operating system (OS) are installed on the hypervisor. Type 1 hypervisor has direct access to the hardware resources. Therefore they are more efficient than hosted architectures. Some examples of type 1 hypervisor are VMware vSphere/ESXi, Oracle VM Server, KVM and Microsoft Hyper-V.

In contrast to type 1 hypervisor, a type 2 hypervisor (or hosted hypervisor) runs on top of an operating system and not the physical hardware directly. A big advantage of Type 2 hypervisors is that management console software is not required. Examples of type 2 hypervisor are VMware Workstation (which can run on Windows, Mac and Linux) or Microsoft Virtual PC (only runs on Windows).

Type1_Type2_Hypervisors.jpg

Question 5

Explanation

Server virtualization and the use of virtual machines is profoundly changing data center dynamics. Most organizations are struggling with the cost and complexity of hosting multiple physical servers in their data centers. The expansion of the data center, a result of both scale-out server architectures and traditional “one application, one server” sprawl, has created problems in housing, powering, and cooling large numbers of underutilized servers. In addition, IT organizations continue to deal with the traditional cost and operational challenges of matching server resources to organizational needs that seem fickle and ever changing.

Virtual machines can significantly mitigate many of these challenges by enabling multiple application and operating system environments to be hosted on a single physical server while maintaining complete isolation between the guest operating systems and their respective applications. Hence, server virtualization facilitates server consolidation by enabling organizations to exchange a number of underutilized servers for a single highly utilized server running multiple virtual machines.

By consolidating multiple physical servers, organizations can gain several benefits:
+ Underutilized servers can be retired or redeployed.
+ Rack space can be reclaimed.
+ Power and cooling loads can be reduced.
+ New virtual servers can be rapidly deployed.
+ CapEx (higher utilization means fewer servers need to be purchased) and OpEx (few servers means a simpler environment and lower maintenance costs) can be reduced.

Reference: https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/net_implementation_white_paper0900aecd806a9c05.html

Question 6

Explanation

A virtual machine (VM) is a software emulation of a physical server with an operating system. From an application’s point of view, the VM provides the look
and feel of a real physical server, including all its components, such as CPU, memory, and network interface cards (NICs).

The virtualization software that creates VMs and performs the hardware abstraction that allows multiple VMs to run concurrently is known as a hypervisor.

There are two types of hypervisors: type 1 and type 2 hypervisor.

In type 1 hypervisor (or native hypervisor), the hypervisor is installed directly on the physical server. Then instances of an operating system (OS) are installed on the hypervisor. Type 1 hypervisor has direct access to the hardware resources. Therefore they are more efficient than hosted architectures. Some examples of type 1 hypervisor are VMware vSphere/ESXi, Oracle VM Server, KVM and Microsoft Hyper-V.

In contrast to type 1 hypervisor, a type 2 hypervisor (or hosted hypervisor) runs on top of an operating system and not the physical hardware directly. A big advantage of Type 2 hypervisors is that management console software is not required. Examples of type 2 hypervisor are VMware Workstation (which can run on Windows, Mac and Linux) or Microsoft Virtual PC (only runs on Windows).

Type1_Type2_Hypervisors.jpg

Question 7

Question 8

Explanation

Because some PE routers might receive routing information they do not require, a basic requirement is to be able to filter the MP-iBGP updates at the ingress to the PE router so that the router does not need to keep this information in memory.

The Automatic Route Filtering feature fulfills this filtering requirement. This feature is available by default on all PE routers, and no additional configuration is necessary to enable it. Its function is to filter automatically VPN-IPv4 routes that contain a route target extended community that does not match any of the PE’s configured VRFs. This effectively discards any unwanted VPN-IPv4 routes silently, thus reducing the amount of information that the PE has to store in memory -> Answer D is correct.

Reference: MPLS and VPN Architectures Book, Volume 1

The reason that PE1 dropped the route is there is no “route-target import 999:999” command on PE1 (so we see the “DENIED due to:extended community not supported” in the debug) so we need to type this command to accept this route -> Answer E is correct.

Comments
  1. Anonymous
    March 17th, 2020

    Are this questions in the current exam?

  2. jlai
    May 31st, 2020

    @digitaltut Hello, please add Q8 on the quizzes thank you

  3. jlai
    May 31st, 2020

    @digitaltut I think you need to update other questions on the quizzes some are not available in the quizzes and there are some questions on the quizzes are not on the site. thanks.

  4. digitaltut
    May 31st, 2020

    @jlai: We have just optimized some topics (Virtualization, Miscellaneous and LISP VXLAN Questions) so some of the questions have been swapped. We have just updated all of them so please try again!

  5. fakus
    June 8th, 2020

    question number 1 , is the answer not A ??

  6. Heamgu
    June 18th, 2020

    Question 3

    Which two statements about VRF-lite are true? (Choose two)
    A. It can increase the packet switching rate
    B. It supports most routing protocols, including EIGRP, ISIS, and OSPF
    C. It supports MPLS-VRF label exchange and labeled packets
    D. It should be used when a customer’s router is connected to an ISP over OSPF
    E. It can support multiple customers on a single switch

    Answer is D and E

    Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/vrf.html#wp1045190

  7. OniWAbaN
    July 7th, 2020

    @digitaltut

    Question 3

    Answer is D and E

    – VRF-lite does not support IGRP and ISIS.
    – The capability vrf-lite subcommand under router ospf should be used when configuring OSPF as the routing protocol between the PE and the CE.

    Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/vrf.html#wp1045190

  8. digitaltut
    July 8th, 2020

    @Heamgu, @OniWAbaN: Thanks for your detection, we have just updated Q.3.

  9. OniWAbaN
    July 13th, 2020

    @digitaltut Question 3 in Quiz doesn’t update.

  10. Syed
    July 26th, 2020

    @digitaltut Question 3 in Quiz doesn’t update.

  11. Thamurt
    July 26th, 2020

    Question 1 : A on avis c’est plutôt D.

  12. Josh
    August 11th, 2020

    Hello, there are different answers in dumps:

    What are two reasons why broadcast radiation is caused in the virtual machine environment?
    (Choose two)

    A. vSwitch must interrupt the server CPU to process the broadcast packet
    B. The Layer 2 domain can be large in virtual machine environments
    C. Virtual machines communicate primarily through broadcast mode
    D. Communication between vSwitch and network switch is broadcast based
    E. Communication between vSwitch and network switch is multicast based

    Which two are the correct ones?

    Regards.

  13. AJ
    August 21st, 2020

    I believe the answer should be A&D

  14. SaniBani
    August 23rd, 2020

    Can someone confirm what is correct answer?

    What are two reasons why broadcast radiation is caused in the virtual machine environment? (Choose two)
    A. vSwitch must interrupt the server CPU to process the broadcast packet
    B. The Layer 2 domain can be large in virtual machine environments
    C. Virtual machines communicate primarily through broadcast mode
    D. Communication between vSwitch and network switch is broadcast based
    E. Communication between vSwitch and network switch is multicast based
    Answer: A C or A D?

  15. As
    September 9th, 2020

    Question 3
    Which two statements about VRF-lite are true? (Choose two)
    A. It can increase the packet switching rate
    B. It supports most routing protocols, including EIGRP, ISIS, and OSPF
    C. It supports MPLS-VRF label exchange and labeled packets
    D. It should be used when a customer‘s router is connected to an ISP over OSPF
    E. It can support multiple customers on a single switch
    I believe the answer should be B, E

  16. Nick
    September 24th, 2020

    @As

    VRF-lite does not support IGRP and ISIS. You can find the answer in this link:

    https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/vrf.html#wp1045190

  17. Nick
    September 24th, 2020

    @AS

    So B would not have been the answer. The correct options are D & E.

  18. Joker
    October 15th, 2020

    For this:

    What are two reasons why broadcast radiation is caused in the virtual machine environment? (Choose two)
    A. vSwitch must interrupt the server CPU to process the broadcast packet
    B. The Layer 2 domain can be large in virtual machine environments
    C. Virtual machines communicate primarily through broadcast mode
    D. Communication between vSwitch and network switch is broadcast based
    E. Communication between vSwitch and network switch is multicast based

    Answer is: A & B.

    Source:

    Because the vswitch is software based, as broadcasts are received the vswitch must interrupt the server CPU to change contexts to enable the vswitch to process the packet. After the vswitch has determined that the packet is a broadcast, it copies the packet to all the VMNICs, which then pass the broadcast packet up the stack to process. This processing overhead can have a tangible effect on overall server performance if a single domain is hosting a large number of virtual machines.

    https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/net_implementation_white_paper0900aecd806a9c05.html

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