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This example demonstrates how to configure a Site-to-Site IPSec VPN with Strongswan and SSL certificates. The example was tested and verified using Fedora VMs in GNS3.
Install the strongswan package from fedora package repository.
dnf install -y strongswan
Configure a network interface for the WAN connection between VPNs and a network interface for the LAN host network.
nmcli connection add ifname ens4 connection.id wan connection.type 802-3-ethernet mtu 1460 ipv4.method manual ipv4.address 100.64.20.1/30 nmcli connection add ifname ens5 connection.id lan connection.type 802-3-ethernet ipv4.method manual ipv4.address 192.168.80.1/24 mtu 1460
nmcli connection add ifname ens4 connection.id wan connection.type 802-3-ethernet mtu 1460 ipv4.method manual ipv4.address 100.64.20.2/30 nmcli connection add ifname ens5 connection.id lan connection.type 802-3-ethernet ipv4.method manual ipv4.address 192.168.90.1/24 mtu 1460
Generate and sign certificates and private keys for both VPN sites.
Copy the CA certificate, VPN certificate, and private key.
cp <ca_cert> /etc/strongswan/ipsec.d/cacerts/ cp <vpn_cert> /etc/strongswan/ipsec.d/certs/ cp <vpn_key> /etc/strongswan/ipsec.d/private/
/etc/srongswan/ipsec.conf
config setup charondebug="all" uniqueids=yes strictcrlpolicy=no conn %default conn tunnel-to-site-2 left=100.64.20.1 leftsubnet=192.168.80.0/24 right=100.64.20.2 rightsubnet=192.168.90.0/24 ike=aes256-sha2_256-modp1024! esp=aes256-sha2_256! keyingtries=0 lifetime=1h lifetime=8h dpddelay=30 dpdtimeout=120 dpdaction=restart auto=start fragmentation=yes keyexchange=ikev2 type=tunnel leftcert=vpn1cert.pem leftid="C=US, ST=Michigan, L=Livonia, O=KobaNet, OU=NetOps, CN=vpn1.koba.ninja" rightid="C=US, ST=Michigan, L=Livonia, O=KobaNet, OU=NetOps, CN=vpn2.koba.ninja"
/etc/strongswan/ipsec.secrets
: RSA vpn1key.pem
/etc/srongswan/ipsec.conf
config setup charondebug="all" uniqueids=yes strictcrlpolicy=no conn %default conn tunnel-to-site-2 left=100.64.20.2 leftsubnet=192.168.90.0/24 right=100.64.20.1 rightsubnet=192.168.80.0/24 ike=aes256-sha2_256-modp1024! esp=aes256-sha2_256! keyingtries=0 lifetime=1h lifetime=8h dpddelay=30 dpdtimeout=120 dpdaction=restart auto=start fragmentation=yes keyexchange=ikev2 type=tunnel leftcert=vpn1cert.pem leftid="C=US, ST=Michigan, L=Livonia, O=KobaNet, OU=NetOps, CN=vpn2.koba.ninja" rightid="C=US, ST=Michigan, L=Livonia, O=KobaNet, OU=NetOps, CN=vpn1.koba.ninja"
/etc/strongswan/ipsec.secrets
: RSA vpn2key.pem
Start the VPN.
strongswan start