AWS Solutions Architect/training/Section 5: Advanced Amazon VPC: Difference between revisions

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 **AWS CloudFront is a CDN with 13+ Regional Edge Caches and 400+ Edge locations.
 *44. Defining VPC CIDR Blocks
+**8 host bits = 256 addresses /24 subnet mask 255.255.255.0
+**16 host bits = 65,536 addresses /16 subnet mask 255.255.0.0
+**12 host bits = 4096 addresses /20 subnet mask <ref>https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#IPv4_CIDR_blocks</ref>
+**Cannot increase or decrease the size of your CIDR block once it's defined (You'd have to create and migrate to a new VPC)
+**Recommended to use RFC 1918 ranges <ref>The Internet Assigned Numbers Authority (IANA) has reserved the
+   following three blocks of the IP address space for private internets:
+.0.0.0        -   10.255.255.255  (10/8 prefix)
+.16.0.0      -   172.31.255.255  (172.16/12 prefix)
+.168.0.0     -   192.168.255.255 (192.168/16 prefix)
+We will refer to the first block as "24-bit block", the second as
+   "20-bit block", and to the third as "16-bit" block. Note that (in
+   pre-CIDR notation) the first block is nothing but a single class A
+   network number, while the second block is a set of 16 contiguous
+   class B network numbers, and third block is a set of 256 contiguous
+   class C network numbers.</ref>
+**https://docs.aws.amazon.com/vpc/latest/userguide/subnet-sizing.html
+**Solarwinds has an interactive (not obvious) calculator https://www.solarwinds.com/free-tools/advanced-subnet-calculator
 *45. [HOL] Create a Custom VPC
 *46. VPC Routing Deep Dive
@@ Line 19: / Line 42: @@
 *55. VPC Endpoints
 *56. [HOL] Create VPC Endpoint
+<br />{{References}}