Note_Tech

All technological notes.

---

Project maintained by simonangel-fong Hosted on GitHub Pages — Theme by mattgraham

AWS - VPC

Back

• AWS - VPC
  • AWS VPC
    • Hands-on
  • Default VPC Walkthrough
    • Hands-on
  • Subnet
    • Hands-on

---

AWS VPC

• VPC / Virtual Private Cloud

• You can have multiple VPCs in an AWS region (max. 5 per region – soft limit)

• Max. CIDR per VPC is 5, for each CIDR:

  • Min. size is /28 (16 IP addresses)
  • Max. size is /16 (65536 IP addresses)

• Because VPC is private, only the Private IPv4 ranges are allowed:

  • 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
  • 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
  • 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)

• Your VPC CIDR should NOT overlap with your other networks (e.g., corporate)

---

• max 5 VPC / region
• max 5 CIDR / VPC
• /16 - /28 / CIDR

• Sample:
  • You have a corporate network of size 10.0.0.0/8 and a satellite office of size 192.168.0.0/16. Which CIDR is acceptable for your AWS VPC if you plan on connecting your networks later on?
    • 172.16.0.0/16
    • CIDR not should overlap(排除其他选项), and the max CIDR size in AWS is /16.

---

Hands-on

• Create VPC

• Add CIDR
  • up to 5

---

Default VPC Walkthrough

• 172.16.0.0/12
• All new AWS accounts have a default VPC
• New EC2 instances are launched into the default VPC if no subnet is specified

• Default VPC

  • has Internet connectivity
  • all EC2 instances inside it have public IPv4 addresses
• We also get a public and a private IPv4 DNS names

---

Hands-on

• Default VPC
  • 173.16.0.0/12

• Subnet
  • each subnet has its CIDR

• 4091(5 are missing)

---

Subnet

• AWS reserves 5 IP addresses (first 4 & last 1) in each subnet

  • These 5 IP addresses are not available for use and can’t be assigned to an EC2 instance

• e.g.: if CIDR block 10.0.0.0/24, then reserved IP addresses are:

  • 10.0.0.0 – Network Address
  • 10.0.0.1 – reserved by AWS for the VPC router
  • 10.0.0.2 – reserved by AWS for mapping to Amazon-provided DNS
  • 10.0.0.3 – reserved by AWS for future use
  • 10.0.0.255 – Network Broadcast Address. AWS does not support broadcast in a VPC, therefore the address is reserved

• Exam Tip, if you need 29 IP addresses for EC2 instances:

  • You can’t choose a subnet of size /27 (32 IP addresses, 32 – 5 = 27 < 29)
  • You need to choose a subnet of size /26 (64 IP addresses, 64 – 5 = 59 > 29)

• Sample:
  • You plan on creating a subnet and want it to have at least capacity for 28 EC2 instances. What’s the minimum size you need to have for your subnet?
    • /26
    • 2^(32-26) -5 > 28
  • AWS reserves 5 IP addresses each time you create a new subnet in a VPC. When you create a subnet with CIDR 10.0.0.0/24, the following IP addresses are reserved, EXCEPT ………………..
    • 0,1,2,3,255

---

Hands-on

• Create new subnet

• Create 2 public subnet

• Create 2 private subnet

• Warning if overlap

• result

• Note:

  • the settings above is the same
  • Diff between public IP and Private IP is whether Auto-assign IP settings is enable

• By default, Auto-assign IP settings is disable.

  • if want to auto-assign IP within a subnet, need enable manually.

---

TOP