Chapter 44 - Cloud Architecture

Question 1

What are the characteristics of a Cloud Computing service?

Answer 1

• Can be requested on demand - The consumer can action changes as required without requiring interaction with the provider
• Can dynamically scale (it is elastic) at will so it appears to the consumer as if the resources are unlimited
• Uses a pool of resources, rather than dedicated specific servers to specific customers, and dynamically allocates resources from that pool for each customer request
• Has a variety of network access options - Can be accessed from multiple different network options (e.g. Private WAN, Internet, MPLS VPN)
• Can be measured and billed back to the customer based on the amount used

Question 2

What is a KVM?

Answer 2

• Keyboard, Video Display, Mouse
• Normally a server could be characterised as no KVM since they are administered remotely

Question 3

What is Cisco’s range of Blade devices called?

Answer 3

• UCS B series (Unified Computing System Blade series)
• UCS is their server range

Question 4

What is a VM?

Answer 4

• Virtual Machine
• A virtual instance of an OS hosted on a server
• Multiple can be hosted on a single server instead of dedicating one hardware server to each instance

Question 5

What is Multithreading?

Answer 5

• The ability for a CPU core to run multiple tasks at once

Question 6

What is a Hypervisor?

Answer 6

• Also known as a VMM (Virtual Machine Monitor)
• Manages and allocates hardware resources to VMs based on their settings

Question 7

What is the relationship between a vSwitch and vNICs?

Answer 7

• A vSwitch is a virtual device that allows a network to form between vNICs
• Neither of these are physical devices
• Normally there is a vNIC per VM but there may only be 1 or 2 physical NICs

Question 8

What are ToR and EoR switches?

Answer 8

• Top of Rack - Found in a data centre, this would be a switch that sits at the top of a rack and acts similarly to an Access switch. It allows the rest of the devices in the rack to connect to the rest of the data centre LAN. Normally the devices in the rack connect to two ToR switches for redundancy
• End of Row - Found in a data centre, this would be a switch that sits at the end of a row of racks and acts similarly to a Distribution switch. It connects all of the Top of Rack switches together and to the rest of the data centre LAN. Normally the ToR switches connect to two EoR switches for redundancy

Question 9

Key points about virtualisation in data centres

Answer 9

• The OS is decoupled from the hardware it runs on so that the OS as a VM can run on any other server in the data centre that has enough resources
• The virtualisation software can automatically start and move VMs between servers in the data centre
• Data centre networking includes vSwitches and vNICs within each server
• Data centre networking can be programmsed by the virtualisation software allowing new VMs to be configured, started, moved, and stopped, with the network details being configured automatically

Question 10

What are other names for Private Cloud and Public Cloud?

Answer 10

• Private Cloud - On-Premise (Although it may not be on-premises)
• Public Cloud - Cloud

Question 11

What is a Private Cloud service?

Answer 11

• A cloud service created and utilised by a single company. It may be created by a different company for this company.
• May be on or off premises

Question 12

What is a Public Cloud service?

Answer 12

• A cloud service created and administered by a single company and then provided to other companies

Question 13

What is Infrastructure as a Service?

Answer 13

• Also called IaaS
• A consumer pays for the use of a VM hosted on a cloud provider’s hardware. The consumer specifies the resources dedicated to the VM and the Operating System
• Well known examples could be Amazon EC2 and Google Compute Engine

Question 14

What are other terms for “Starting a VM?

Answer 14

• “Spinning up a VM”
• “Instantiating a VM”

Question 15

What is Software as a Service?

Answer 15

• Also called SaaS
• A consumer pays for a bit of software that runs on a VM or multiple VMs. The consumer has no input over the details or resources of the VM(s).
• Well known examples could be iCloud, Google Drive, Dropbox, etc.

Question 16

What is Platform as a Service?

Answer 16

• Also called PaaS
• A consumer pays for the use of VMs hosted on a cloud provider’s hardware (similar to IaaS) to host the consumer’s software such as an IDE. Often utilised by developers. Consumer doesn’t control the OS.
• Well known examples could be AWS Lambda and Google App Engine

Question 17

Pros and Cons of connecting to a Public Cloud via the Internet or an Internet VPN

Answer 17

Pros:
- Agility - Cloud providers will normally already be connected to the internet so there is no need for the consumer to wait for a private WAN to be setup between them and the cloud provider
- Migration - For the same reason as above, an enterprise can switch from one cloud provider to another
- Distributed Users - As long as users can connect to the Internet, they can connect to the cloud service
- (Only if using an Internet VPN) Security - Allows for encryption for data sent over the Internet

Cons:
- Security - Less secure than private WANs (e.g. Man in the middle attacks are possible) unless using an Internet VPN
- Capacity - Moving an internal application to the public cloud increases network traffic so the consumer needs to be sure their current infrastructure can handle it
- QoS - The internet does not provide QoS like private WANs so this could result in a worse user experience with an application that has been moved from internal to public cloud
- No WAN SLA - ISPs normally do not provide SLAs for connectivity to all destinations of a network unlike private WAN providers

Question 18

Pros and Cons of connecting to a Public Cloud via a Private WAN/VPN

Answer 18

Pros:
- Security - No possibility of Man in the Middle attacks and VPNs would send traffic encrypted
- QoS - Private WANs (e.g. MPLS VPN and Ethernet WANs) can provide QoS unlike the Internet

Cons:
- Time - Can take time to install the service
- Cost - Can be costly
- Planning - Requires capacity planning
- Migration - No inherent ease of migration between cloud providers

Question 19

What is an Intercloud Exchange?

Answer 19

• A company that creates a private network as a service
• Connects to multiple cloud providers so that consumers that connect to these exchanges can easily connect to multiple cloud providers
• Useful for migration of cloud based services

Question 20

Pros and Cons of Intercloud Exchanges

Answer 20

Pros:
- Security
- QoS
- Migration - Inherent ease of migration between cloud providers

Cons:
- Time - Can take time to install the Private WAN between the consumer and the exchange
- Planning - Requires capacity planning

Question 21

What are the different types of Hypervisor?

Answer 21

• Type 1 - Runs directly on top of the hardware and not on another OS. Also known as a Bare Metal Hypervisor or Native Hypervisor (Examples are VMWare ESXI, Microsoft Hyper-V). Often used in data centres.
• Type 2 - Runs on an OS like a regular program. Also known as a Hosted Hypervisor (Examples are Oracle VirtualBox, VMWare Workstation). The OS running directly on the hardware (that the Type 2 Hypervisor runs on) is called a Host OS. The OS that the Type 2 Hypervisor manages is called a Guest OS. Often used on personal devices.

Question 22

What are the benefits of using Virtualisation?

Answer 22

• Partitioning - Run multiple OSs on one physical machine and delegate resources between VMs accordingly
• Isolation - Provide fault and security isolation at hardware level and preserve performance with advanced resource controls.
• Encapsulation - Save VMs to files and copy and move them as easy as copying and moving regular files
• Hardware Independence - Provision or migrate any VM to any physical server
• Reduced Cost - Don’t need multiple physical servers

Question 23

What is Colocation?

Answer 23

• When data centres rent out space for customers to put their infrastructure

Question 24

What is a Community Cloud Service?

Answer 24

• Similar to a Private Cloud Service although instead of being utilised by a single company it will only be utilised by a specific group of companies for a common goal.
• May be created by a company in the Community or a third party

Question 25

What is a Hybrid Cloud Service?

Answer 25

- Any combination of Public, Private, and Community Cloud Services. - For example a Private Cloud could offload to a Public Cloud when under a large load

Question 26

What are Containers?

Answer 26

- Software packages that contain apps and all of that app's dependencies that it requires to function. - Multiple apps can be run on a single container but this is not standard practice - Containers run on a Container Engine (e.g. Docker Engine) which runs on a Host OS (e.g. Linux) - Containers are more lightweight than VMs as they only contain data for a specific app to run and run on top of a shared OS.

Question 27

What is a Container Orchestrator?

Answer 27

- A software platform used for automating the deployment, management, and scaling of Containers - The above can be done manually but it becomes more difficult the more Containers that are in use - Examples are Kubernetes or Docker Swarm

Question 28

What is Microservice Architecture?

Answer 28

- The practice of dividing a larger solution into smaller ones called Microservices. These can all run in Containers.

Question 29

Comparison of VMs vs Containers

Answer 29

- VMs generally take longer to boot up than Containers - VMs generally take up more disk space than Containers - VMs generally use more processing power than Containers - VMs are portable but Containers are even more so - VMs are more isolated and therefore an issue with one VM is unlikely to cause issues with another. If an OS running multiple Containers crashes then all of the Containers go too. The isolation also makes VMs more secure.

Question 30

What is VRF?

Answer 30

- Virtual Routing & Forwarding - Used to divide a single physical router into multiple virtual routers by building separate routing tables - Works similarly to VLANs at layer 2 in that: - With VLANs, only devices in the same broadcast domain can communicate at layer 2 - With VRFs, only interfaces in the same VRF can communicate at layer 3 unless VRF Leaking is configured - Layer 3 interfaces are configured to be put into a specific VRF instance. Can not be done with layer 2 interfaces. - Commonly used to facilitate MPLS, however there is also VRF-Lite (VRF without MPLS) - Multiple VRFs can contain the same subnets without an issue.

Question 31

What commands do you use to configure VRFs?

Answer 31

- To create a VRF: 'ip vrf ' in global config mode - To assign an interface to a VRF: 'ip vrf forwarding ' (This will remove the IP address of any interface added to a VRF. The IP address is then configured from VRF config mode)

Question 32

True or False. The 'show ip route' command should show routes within VRFs.

Answer 32

False. 'show ip route' only shows the global routing table. You must use 'show ip route vrf '.

Question 33

What command do you need to use when pinging a device connected to a VRF interface from a router?

Answer 33

'ping vrf '