VPN and Encryption Guide
Table of Contents
Virtual Private Networks (VPN)
Types of VPNs
| Type |
Description |
Use Cases |
| Site-to-Site VPN |
Connects entire networks |
Branch offices, partner networks |
| Remote Access VPN |
Individual client access |
Remote workers, mobile users |
| SSL VPN |
Web-based access |
Secure application access |
| DMVPN |
Dynamic mesh VPN |
Large-scale deployments |
VPN Protocols
Common Protocols:
- IPSec (Internet Protocol Security)
- OpenVPN
- WireGuard
- L2TP/IPSec
- SSTP (Secure Socket Tunneling Protocol)
- IKEv2 (Internet Key Exchange v2)
Encryption Technologies
Symmetric Encryption
| Algorithm |
Key Length |
Security Level |
| AES-256 |
256-bit |
Very High |
| AES-192 |
192-bit |
High |
| AES-128 |
128-bit |
Good |
Asymmetric Encryption
# RSA Key Generation
openssl genrsa -out private.key 4096
openssl rsa -in private.key -pubout -out public.key
# Certificate Generation
openssl req -new -x509 -key private.key -out certificate.crt -days 365
Implementation Guide
Site-to-Site VPN Configuration
# IPSec Configuration Example
crypto isakmp policy 10
encryption aes 256
hash sha256
authentication pre-share
group 14
lifetime 86400
crypto ipsec transform-set TS esp-aes 256 esp-sha-hmac
mode tunnel
crypto map CMAP 10 ipsec-isakmp
set peer 203.0.113.1
set transform-set TS
match address 100
Remote Access VPN Setup
Prerequisites:
- Certificate infrastructure
- Authentication server
- IP address pool
- Access control lists
Security Protocols
Authentication Protocols
- RADIUS
- TACACS+
- LDAP/SSL
- Kerberos
- Certificate-based
Key Exchange
# Diffie-Hellman Groups
Group 14 (2048-bit)
Group 15 (3072-bit)
Group 16 (4096-bit)
Group 19 (256-bit ECP)
Group 20 (384-bit ECP)
Best Practices
VPN Security
- Use strong authentication
- Implement perfect forward secrecy
- Regular key rotation
- Monitor VPN connections
- Implement split tunneling carefully
Encryption Best Practices
1. Key Management
- Secure key storage
- Regular key rotation
- Key backup procedures
- Access control
2. Algorithm Selection
- Use proven algorithms
- Appropriate key lengths
- Modern cipher suites
- Forward secrecy support
Troubleshooting
Common Issues
| Problem |
Possible Cause |
Solution |
| Connection Failed |
Mismatched settings |
Verify phase 1/2 settings |
| Performance Issues |
MTU/fragmentation |
Adjust MTU size |
| Authentication Failure |
Invalid credentials |
Check credentials/certificates |
Diagnostic Commands
# IPSec Troubleshooting
show crypto isakmp sa
show crypto ipsec sa
debug crypto isakmp
debug crypto ipsec
# OpenVPN Debugging
openvpn --status status.log 60
tail -f /var/log/openvpn.log
Performance Optimization:
- Compression settings
- Protocol selection
- MTU optimization
- Hardware acceleration
- Load balancing
Monitoring Tools
# Network Monitoring
iftop -i tun0
tcpdump -i any esp
netstat -rn
# VPN Status
systemctl status openvpn
strongswan statusall