AWS Site-to-Site VPN

MSP Medium
7 min readSep 22, 2023

Similarly create second vpc with public subnet and attach internet-gateway to subnet like above

Vpc2 name:branch

Vpc cidr:10.2.0.0/16

Subnet name:branch

subnet:10.2.1.0/24

Branch Ec2 instance public ip paste down

Then go to mainbranch route table and do as shown below

Wait several minute

You can get all the information in downloaded configuration

Then ssh in branch ec2 with public ip

Open cmd and ssh to branch ec2 instance

sudo su

yum install openswan -y

nano /etc/sysctl.conf

net.ipv4.ip_forward = 1

net.ipv4.conf.default.rp_filter = 0

net.ipv4.conf.default.accept_source_route = 0

nano /etc/ipsec.d/aws.conf

conn Tunnel1

authby=secret

auto=start

left=%defaultroute

leftid=3.89.194.127

right=44.193.242.71

type=tunnel

ikelifetime=8h

keylife=1h

phase2alg=aes128-sha1;modp1024

ike=aes128-sha1;modp1024

keyingtries=%forever

keyexchange=ike

leftsubnet=<LOCAL NETWORK>

rightsubnet=<REMOTE NETWORK>

dpddelay=10

dpdtimeout=30

dpdaction=restart_by_peer

conn Tunnel1

authby=secret

auto=start

left=%defaultroute

leftid=3.89.194.127

right=44.193.242.71

type=tunnel

ikelifetime=8h

keylife=1h

phase2alg=aes128-sha1;modp1024

ike=aes128-sha1;modp1024

auth=esp

keyingtries=%forever

keyexchange=ike

leftsubnet=10.2.0.0/16

rightsubnet=10.1.0.0/16

dpddelay=10

dpdtimeout=30

dpdaction=restart_by_peer

nano /etc/ipsec.d/aws.secret

You can get all the information from downloaded configuration of open swan like below

systemctl start ipsec

systemctl status ipsec

Ssh in branch

ping with mainbranch with private ipv4 addresses its keep running which means your vpn is working

Or you can check it like below

Inside branch ssh

nano mainbranch.pem

Paste the mainbranch.pem

Ctrl+x

Y

Enter

chmod 400 mainbranch.pem

Then ssh with private ip of mainbranch

ssh -i “mainbranch.pem” ec2-user@10.1.1.124

You are inside the branch with mainbranch private ip

Documention by:Gaurav khatiwada

2023 Setember 22

https://www.linkedin.com/in/gaurav-khatiwada-977290176/

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