AWS VPC with Public and Private Subnets, NAT Instance/Bastion Host

Intro - 0:30
Why subnetting - 1:10
Creating a VPC - 7:35
VPC Wizard - 10:18
CIDR & subnets - 12:00
Using VPC Wizard - 17:20
NAT Gateway, NAT Instance, & Bastion Host - 19:00
Elastic IP - 24:30
Connecting to (NAT Instance) Bastion Host - 25:40
Why it doesn't connect - 28:00
Launching an instance in a private subnet - 32:40
Connecting to instance in private subnet - 38:20
SSH Agent Forwarding - 39:35
Allow instances in private subnet access to the Internet - 41:17
Logging in directly to instance in private subnet - 48:50
Shutting down your VPC to avoid charges - 55:45
Assignment intro - 59:30

[hebronspiritualmessages]

Thanks for the well explanation.
i have one doubt here as I'm new to AWS...
when we are able to connect Private instances which are in private subnets via bastion host then what is the need of NAT gateway and NAT instance.. ?
simple we are allowing bastion IP in Private instance SG and connecting from bastion host to private instance.
which is easier than deploying NAT gate and NAT instance...
could pls explain ..

Thanks in advance.

[KarenGoldMind]

thank you im just looking for a Bastion Host explanation and i find a million ways to do it but nothing functionally corretly through Terraform because Terrafomr do some things behind but with this explanation i hope the things go well.

[KarenGoldMind]

I have a question: Wich is the security group of the Ubuntu Private Instance? you only define the route tables but not the Private security group

[SachidanandUpadhyay]

SSH Agent forwarding, I'm used key pair for NAT Bastion and Ubuntu Private server but still issues permission denied for (publickey), I m allow putty to forwarding and load key pair too? can you suggest something