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AWS Professional > 03 Networking > Flashcards

03 Networking Flashcards

1
Q

Describe the two types of AWS services based on accessibility.

A

AWS services can be grouped into public services, which are accessed via a public endpoint (e.g., S3), and private services, which run within a VPC (e.g., EFS).

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2
Q

How can private services be accessed from on-premises environments?

A

A VPN or Direct Connect is required to access private services from on-premises.

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3
Q

Explain how EC2 instances handle their public IPv4 addresses.

A

EC2 instances do not know their own public IPv4 address; this is managed at the gateway, such as the internet gateway.

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4
Q

What is the limitation of NAT regarding IPv6?

A

NAT does not support IPv6.

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5
Q

Define the purpose of Egress-only Internet Gateways.

A

Egress-only Internet Gateways allow instances to connect to the internet while preventing inbound connections.

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6
Q

How many Internet Gateways can be attached to a VPC?

A

Only one Internet Gateway can be attached to a VPC, but both an Internet Gateway and an Egress-only Internet Gateway can be added.

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7
Q

What is the most cost-effective strategy for achieving high availability in AWS?

A

The most cost-effective way to achieve high availability is to deploy across as many Availability Zones (AZs) as possible.

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8
Q

Describe the function of route tables in a VPC.

A

Route tables direct traffic within a VPC, with separate rules for IPv4 and IPv6 traffic.

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9
Q

How does precedence work in route tables?

A

Precedence in route tables is based on selecting the most specific route first, and as a tie breaker, preferring static routes over propagated routes.

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10
Q

What are gateway route tables used for?

A

Gateway route tables are assigned to gateways (e.g., Internet Gateways) to control the routing of ingress traffic.

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11
Q

Explain the encryption of inter-region traffic between peered VPCs.

A

Inter-region traffic between peered VPCs is encrypted.

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12
Q

What is the role of Dynamic Host Configuration Protocol (DHCP) in a VPC?

A

DHCP allows auto-configuration of network resources, including IP, subnet mask, default gateway, DNS server, hostname, NTP, and NetBios settings.

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13
Q

How are DHCP option sets configured in a VPC?

A

DHCP option sets are configured to control DNS servers, domain names, NTP servers, NetBIOS name server, and IPv6 Preferred Lease Time.

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14
Q

What happens when a DHCP option set is associated with a VPC?

A

Associating a DHCP option set takes effect immediately, but changes will only occur when the targets (e.g., EC2 instances) perform a DHCP renew.

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15
Q

Define PrivateLink and its purpose in AWS.

A

PrivateLink allows secure connectivity to AWS services and marketplace services, preventing data from transiting over the public internet.

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16
Q

How do VPC endpoints provide access to AWS services?

A

VPC endpoints provide private access to AWS services, with Gateway Endpoints used specifically for DynamoDB and S3.

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17
Q

What is the function of the prefix list in Gateway Endpoints?

A

The prefix list of the Gateway Endpoint is added to the route table of the VPC to direct traffic to the Gateway Endpoint.

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18
Q

Describe the relationship between Gateway Endpoints and VPCs.

A

Gateway Endpoints are associated with a VPC but do not go into a particular subnet.

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19
Q

Describe the purpose of endpoint policies in AWS.

A

Endpoint policies restrict access to specific resources, such as S3 buckets, and define who can use the endpoint and what resources they can access.

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20
Q

How do Interface Endpoints ensure high availability in AWS services?

A

Interface Endpoints are launched in multiple subnets to ensure high availability.

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21
Q

Define VPC Flow Logs and their function.

A

VPC Flow Logs monitor traffic flow between interfaces in a VPC, capturing only packet metadata and storing logs in S3 or CloudWatch Logs.

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22
Q

Explain the difference between stateful and stateless firewalls in AWS.

A

Stateful firewalls, like security group rules, automatically allow responses to requests, while stateless firewalls, like NACLs, require explicit rules for both inbound and outbound traffic.

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23
Q

How do NACLs manage traffic in a subnet?

A

NACLs control traffic into and out of a subnet with numbered rules, applying lower numbered rules first and denying traffic if no rules match.

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24
Q

Describe the role of WAF in AWS.

A

WAF is a managed application-layer firewall that inspects decrypted HTTPS content and controls traffic through Web ACLs.

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25
Q

What is a Web ACL in the context of AWS WAF?

A

A Web ACL is a unit of configuration in WAF that is attached to resources like ALBs or CloudFront distributions, with default actions set to ALLOW or BLOCK.

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26
Q

How are rules processed in a Web ACL?

A

Rules and Rule Groups added to a Web ACL are processed in order, and each consumes Web ACL Capacity Units (WCU).

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27
Q

What is the maximum number of Web ACL Capacity Units (WCU) allowed per Web ACL?

A

The default maximum is 1500 WCUs per Web ACL, but this can be increased.

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28
Q

Explain how rules in a Web ACL can be defined.

A

Rules can be based on the source of the request, its content, or request volume, with actions that can be Allow, Block, Captcha, or Custom.

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29
Q

How does a security group differ from a NACL in AWS?

A

Security groups are stateful and attached to ENIs, allowing automatic responses, while NACLs are stateless and control traffic at the subnet level.

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30
Q

What happens to traffic if no NACL rules are matched?

A

If no NACL rules are matched, traffic is denied by default.

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31
Q

Describe the significance of ephemeral ports in server connections.

A

Ephemeral ports are used by clients to make requests to servers, and responses are sent back to these ports.

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32
Q

How does a Route53 private hosted zone relate to Interface Endpoints?

A

A Route53 private hosted zone is created automatically to override public records of the service when using Interface Endpoints.

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33
Q

What is the default action for a Web ACL in AWS WAF?

A

The default action for a Web ACL is set to ALLOW or BLOCK.

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34
Q

How many bytes of the body are inspected by WAF rules?

A

Only the first 8192 bytes of the body are inspected by WAF rules.

35
Q

Describe the purpose of the x-amzn-waf header in requests.

A

The x-amzn-waf header is added to requests to influence other rules within the same WebACL.

36
Q

How can logs be stored in AWS for traffic management?

A

Logs can be stored in S3, CloudWatch Logs, and Kinesis, with Kinesis recommended for rapidly responding to traffic.

37
Q

Define Local Zones in the context of AWS infrastructure.

A

Local Zones are extensions of regions that allow for edge computing and are associated with a parent region.

38
Q

What is the role of Direct Connect in relation to Local Zones?

A

Direct Connect allows connectivity from on-premises to the Local Zone.

39
Q

How do subnets function in Local Zones?

A

Subnets can be created in Local Zones, extending VPCs into the Local Zone.

40
Q

Explain how BGP determines the best route.

A

BGP uses the shortest connection, or least hops, by default to determine the best route.

41
Q

What workaround can be used in BGP to influence route selection?

A

Dummy hops can be added to make a route appear slower, influencing BGP to select it.

42
Q

Describe the function of Global Accelerator in network performance.

A

Global Accelerator improves network performance for users far from the host by routing traffic to the closest edge location using any-cast IP addresses.

43
Q

How does Global Accelerator differ from CloudFront?

A

Global Accelerator moves the connection to the edge for all TCP/UDP traffic, while CloudFront caches content at the edge for HTTP content only.

44
Q

What is the purpose of a Transit Gateway in AWS networking?

A

A Transit Gateway is a networking hub that connects VPCs together and to on-premises networks using Site-to-Site VPNs and Direct Connect.

45
Q

How are Transit Gateways configured?

A

Transit Gateways are configured by creating attachments to VPCs, Site-to-Site VPNs, or Direct Connect.

46
Q

Explain the advantage of using Transit Gateways over manual VPC connections.

A

Transit Gateways simplify networking by avoiding the need for non-transitive peering connections, which would require many routes.

47
Q

What is the default routing behavior of a Transit Gateway?

A

Each Transit Gateway has a default routing table that includes all attachments, allowing every attachment to connect with each other.

48
Q

What limitations exist regarding route propagation in Transit Gateways?

A

Route propagation and DNS sharing are not supported across Peering Attachments in Transit Gateways.

49
Q

Define Client VPN in the context of hybrid networking.

A

Client VPN allows end-users to connect to private networking in a VPN and is a managed implementation of OpenVPN.

50
Q

How does the split tunnel option work in Client VPN?

A

The split tunnel option allows only internal traffic to use the VPN, leaving connections from the client to the internet unaffected.

51
Q

What is IPSec and its primary function?

A

IPSec is a set of protocols used to establish a secure tunnel across insecure networks, ensuring all traffic is encrypted in transit.

52
Q

Describe the encryption process used in IPSec.

A

IPSec uses asymmetric encryption to securely establish a shared key, which is then used for faster symmetric encryption.

53
Q

What are the two phases of IPSec?

A

The two phases of IPSec are IKE Phase 1, which authenticates the connection and establishes a shared key, and IKE Phase 2, which agrees on the encryption method and keys for bulk data transfer.

54
Q

Describe the purpose of a Phase 2 tunnel in AWS Site-to-Site VPN.

A

A Phase 2 tunnel is established much quicker than a Phase 1 tunnel and is commonly used while the Phase 1 tunnel remains active as needed.

55
Q

Define the role of the Virtual Private Gateway (VGW) in AWS.

A

The Virtual Private Gateway (VGW) serves as the mounting point for the VPN within the VPC.

56
Q

How is high availability achieved in AWS Site-to-Site VPN?

A

High availability is achieved by having two endpoints in two availability zones, although both tunnels terminate at a single customer router, which does not provide full HA on the customer side.

57
Q

Explain the function of the Customer Gateway (CGW) in AWS networking.

A

The Customer Gateway (CGW) refers to the target in the customer’s network for the VPN connection.

58
Q

What is the maximum throughput for a VPN with two tunnels in AWS?

A

The maximum throughput for a VPN with two tunnels is 1.25 Gbps.

59
Q

Describe the use of Dynamic VPNs in AWS.

A

Dynamic VPNs use BGP to route between AWS and the customer router, allowing for failover and are required when using Direct Connect.

60
Q

How does the Accelerated Site-to-Site VPN improve network performance?

A

The Accelerated Site-to-Site VPN uses Global Accelerator to enhance network performance.

61
Q

Define Hybrid DNS in the context of AWS.

A

Hybrid DNS is implemented using Route53 endpoints, which include inbound and outbound endpoints for managing DNS queries.

62
Q

What is the significance of the .2 IP address in AWS subnets?

A

The .2 IP address of every subnet is reserved for the Route53 resolver.

63
Q

Explain the function of NS records in DNS.

A

NS (name server) records delegate authority to other registries, such as delegating amazon.com to Amazon’s DNS servers.

64
Q

What are Alias Records in Route53, and how do they differ from CNAME records?

A

Alias Records are a Route53-specific record type that map a name to an AWS record and can be set at the apex domain without incurring charges, unlike CNAME records.

65
Q

How can a domain registered with a third-party provider be used in Route53?

A

To use a domain registered with a third-party provider in Route53, NS records must be added through that provider, pointing to the Route53 name servers.

66
Q

Describe the concept of private hosted zones in AWS.

A

Private hosted zones can only be accessed from VPCs they are attached to, and they can replace public hosted zones with the same name in a split-view configuration.

67
Q

What is the role of Route53 in AWS?

A

Route53 is a managed DNS service that handles both private and public DNS records.

68
Q

How does latency affect AWS Site-to-Site VPN connections?

A

Latency may be higher in AWS Site-to-Site VPN connections due to the use of the public internet and the number of hops involved.

69
Q

What is the purpose of TTL in DNS records?

A

TTL (time to live) indicates when DNS records expire, helping to manage caching and refresh intervals.

70
Q

How many Transit Gateways can one Direct Connect gateway connect with?

A

One Direct Connect gateway can connect with up to 3 Transit Gateways.

71
Q

Describe the purpose of health checks in VPC endpoints.

A

Health checks monitor the health and performance of a target, ensuring that the service is operational and responsive.

72
Q

How often are health checks performed by default, and what is the alternative configuration?

A

By default, health checks are performed every 30 seconds, but they can be configured to occur every 10 seconds for an additional charge.

73
Q

Define the types of checks that can be performed in health checks.

A

Checks can be performed to an endpoint, for a CloudWatch Alarm, or calculated checks (checks of checks).

74
Q

What are the criteria for HTTP/HTTPS health checks?

A

HTTP/HTTPS checks confirm that the status code is between 200-399 and can ensure that a certain string is present in the response body.

75
Q

Explain the Simple routing type in VPC endpoints.

A

Simple routing creates one record per name, which can have multiple values (IP addresses) returned in random order, but it does not support health checks.

76
Q

Describe the Failover routing type and its functionality.

A

Failover routing directs all queries to the primary resource unless it fails its health checks, in which case the secondary resource is used, allowing for automated active-passive failover.

77
Q

What is the Multi-value routing type in VPC endpoints?

A

Multi-value routing returns up to eight healthy records in a random order.

78
Q

How does Weighted routing work in VPC endpoints?

A

Weighted routing assigns a weight to each record, controlling the likelihood of that record being returned, which can be used for load balancing and canary testing.

79
Q

Define Latency routing and its purpose.

A

Latency routing adds one record per region and returns the record from the region the client can reach with the lowest latency, optimizing for performance and user experience.

80
Q

What is the Geolocation routing type in VPC endpoints?

A

Geolocation routing assigns records to specific continents, countries, and U.S. states, returning relevant records while preferring specificity.

81
Q

Explain the Geoproximity routing type.

A

Geoproximity routing assigns records to locations and returns the closest record(s) to the client, with a bias that can increase or decrease the influence of a location.

82
Q

What roles can Route53 serve in DNS management?

A

Route53 can act as a registrar-only or DNS host only, meaning its name servers can host the zone for a domain registered elsewhere.

83
Q

Define DNSSEC and its purpose in DNS records.

A

DNSSEC adds signatures to DNS records, allowing clients to verify that the records were not tampered with in transit.

84
Q

How is DNSSEC implemented in VPC endpoints?

A

An asymmetric key pair in KMS is used for signing, and a delegated signer record is added to the next level down, continuing a hash of the zone’s public key.

AWS Professional (10 decks)

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