Route 53

DNS 101

  1. What is DNS? : DNS is used convert human friendly domain names into IP address
  2. IP address : Ipv4 is a 32 bit address and Ipv6 128 bit address
  3. Domains :
    1. Top level domains: .com, .org, .gov . IANA controls these domains in root zone database.
    2. second level domain names : co.uk , co.in
  4. Domain Registrar: Godaddy,Bluehost,Hostgator . Recently, Amazon also became a domain registrar.
  5. SOA Records
    1. The name of the server that supplied the data for the zone
    2. Administrator of the zone
    3. Current version of data file
    4. # of seconds secondary domain server should wait before checking updates
    5. # of seconds secondary domain server should wait before retrying a failed zone transfer
    6. # of seconds secondary domain server can use data before it must be either refreshed or expire
    7. The default # of seconds for the time to live (ttl) file on resource records
  6. Name Server (NS) Records
    1. Used by top level domain name servers to direct traffic to the content DNS server which contains the authoritative DNS records.
  7. Address (A) record:
    1. Translate domain name to IP Address
  8. Time to live (TTL)
    1. # Of seconds that a DNS record is cached in resolving server or client PC.
    2. Lower the TTL faster the changes to DNS records are propogated
  9. Canonical Name (cname):
    1. Resolve one domain name to another domain name ( example : www.mobile.nxgcloud.com resolves to www.m.nxgcloud.com)
  10. Alias records :
    1. Amazon created. Specific to route 53
    2. naked domains/ zone apex record to ELB/S3/CDN. cname records cannot be used for naked domains , but alias can be used
  11. Exam tips:
    1. ELB’s do not have pre-defined IPV4 addresses. Resolve them using DNS names.
    2. Understand the difference between cname and Alias
    3. Given a choice , choose Alias records over cname records

Register a Domain Name

  1. Route53 ->Domains -> Register domains (Options: register domain name or transfer domain name)
  2. Select register domain name -> choose a domain name->Add to cart->Fill the contact details->Complete purchase
  3. Wait for the registration to be completed
  4. By default , NS and SOA records will be created in zone

Routing Policies

  1. Simple
    1. Default routing policy
    2. Single record set in routing policy
    3. Use case: your domain is served by single resource. (e.g. Website is served by single EC2 instance/Single ELB)
    4. No built in intelligence
  2. Weighted
    1. Multiple record sets in routing policy. Assign weight to each record set
    2. Traffic is split based on weights assigned to the record sets.
    3. Example.
      1. Record1: nxgcloud.com -> Target ELB1 weight 80%
      2. Record2: nxgcloud.com -> Target ELB2 weight 20%
      3. Traffic coming to nxgcloud.com will be split between ELB1 and ELB2. 80% traffic to ELB1 , 20% to ELB2
    4. Usecase: Testing your development servers before putting them into production
  3. Latency
    1. Multiple record sets in routing policy. Specify region to each record set
    2. Traffic is split based on lowest latency for the end user
    3. Example.
      1. Record1: nxgcloud.com -> Target ELB1 Region R1 ( EU-West-2)
      2. Record2: nxgcloud.com -> Target ELB2 Region R2 (Ap-Southeast-2)
      3. Traffic coming to nxgcloud.com will be routed based on latency. When a request comes to the domain AWS selects the target in region with lowest latency for the end user
    4. Usecase: Production workload to improve the page load times for users scattered across the world.
  4. Fail over
    1. Multiple record sets in routing policy. Specify failover record type Primary/Secondary
    2. Create health check for active target in Route53
    3. Create Primary record and health check
    4. Create Secondary record
    5. Traffic is always to primary as long as health check is green to it.
    6. Example.
      1. Record1: nxgcloud.com -> Target ELB1 Primary
      2. Record2: nxgcloud.com -> Target ELB2 Secondary
      3. Traffic coming to nxgcloud.com will always goes to ELB1 (Primary). If active site is down traffic will be routed to passive site
    7. Usecase: Active-Passive setup
  5. Geolocation
    1. Multiple record sets in routing policy. Specify location to each record set
    2. Traffic is routed based on geographic location of the end user
    3. Example.
      1. Record1: nxgcloud.com -> Target ELB1 Location Europe
      2. Record2: nxgcloud.com -> Target ELB2 Location US
      3. Record2: nxgcloud.com -> Target ELB3 Location Default
      4. Traffic coming to nxgcloud.com will be routed based on location of the end user.
    4. Usecase: European customers to Europe region US customers to US region.
  6. Exam Tips
    1. ELBs do not have predefined IPV4 addresses. Resolve them using DNS name
    2. Understand the difference between cname and alias records
    3. Given the choice always choose alias
    4. Remember different routing policies and use cases
    5. Supported records
      1. A
      2. AAAA
      3. CNAME
      4. MX
      5. NAPTR
      6. NS
      7. PTR
      8. SOA
      9. SPF
      10. SRV
      11. TXT
    6. Route53 limits

      http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/DNSLimitations.html

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