Implementing Virtual Private Networks

Implementing Virtual Private Networks

1. A VPN is a private network that is created over a public network, usually the Internet.

   • Cost Savings
   • Security
   • Compatibility
   • Scalability
   • Two Types of VPNs
     • Remote Access (Dynamic)
       • Changes dynamically depending on the location of the telecommuter.
     • Site to Site (Static)
       • Hosts send and receive normal TCP/IP traffic through a VPN gateway, which can be a router, firewall, Cisco VPN concentrator, or Cisco ASA.
   • Hairpinning and split tunneling

2. IPsec

   • Is an IETF standard that defines how a VPN can be secured across IP networks.
   • Confidentiality is achieved by encrypting the data.
   • Data integrity means that the data that is received is exactly the same data that was sent.
   • Authenication. When conducting business long distance, it is necessary to know who is at the other end of the phone, email, or fax.
   • Secure Key Exchange. Encryption algorithms require a symmetric, shared secret key to perform encryption and decryption.
   • AH
     • Achieves authenticity by applying a keyed one-way hash function to the packet to create a hash or message digest.
     • Transport Mode
   • ESP
     • Provides confidentiality by encrypting the payload.
     • Tunnel Mode
   • The IKE Protocol
     • Implements key exchange protocols

3. Existing ACL configurations

   • Permit ISAKMP traffic
   • Permit ESP traffic
   • Permit AH traffic

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