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VPN - CCIE - Coggle Diagram

- - - - IKEv1
        
        Phase 1: Establishing the IKE SA
        
        Aggressive Mode
        
        States
        
        AG_INIT: Initiator sends policy, DH exchange, and ID in one packet.
        
        AG_REPLY: Responder sends matching policy, its DH exchange, ID, and authentication proof.
        
        AG_AUTH: Initiator responds with final authentication proof; state transitions to active.
        
        Aggressive Mode compresses Phase 1 into three total messages for faster remote-access connection, though it exposes endpoint identities before encryption finishes
        
        Main Mode
        
        States
        
        MM_NO_STATE: Starting baseline; no messages exchanged yet.
        
        MM_SA_SETUP: Messages 1 and 2 complete; security policies and proposals match.
        
        MM_KEY_EXCH: Messages 3 and 4 complete; Diffie-Hellman public values and nonces exchange.
        
        MM_KEY_AUTH: Messages 5 and 6 complete; peer identities and authentications verify.
        
        MM_ACTIVE / ACTIVE: Tunnel is fully up and functional.
        
        Main Mode uses six clear-text and encrypted messages split into three round trips.
        
        Phase 2: Quick Mode
        
        States
        
        QM_IDLE: Starting or resting state.
        
        QM_AUTH_RQST: First/second messages sent to negotiate traffic selectors, nonces, and optional PFS (Perfect Forward Secrecy).
        
        QM_ACTIVE: Third message completes; IPsec data channels become active.
      - IKEv2
        
        States
        
        Core States and PhasesIdle / Null State: No SA exists. The initiator prepares the first request packet.
        
        IKE_SA_INIT Exchange: Peers exchange crypto algorithms, nonces, and Diffie-Hellman values. The state shifts to negotiating key material.
        
        IKE_AUTH Exchange: Peers prove identity using certificates, pre-shared keys, or EAP, and set up the first IPsec Child SA. The IKE SA becomes fully established.
        
        Established State: Data flows through the tunnel. Triggers active background states like Dead Peer Detection (DPD) or MOBIKE.
        
        CREATE_CHILD_SA State: Used dynamically to rekey the main IKE SA or create/rekey new Child SAs.
        
        Delete / Closing State: Tear-down notifications clear states and release security parameters from memory.
    - - Parameter
        
        Encryption Algorithm: Safeguards data privacy (e.g., AES).
        
        Hash/Authentication Algorithm: Ensures data integrity (e.g., SHA-256).
        
        Diffie-Hellman (DH) Group: Defines how secret keys are exchanged safely.
        
        Lifetime: Specifies when keys expire and must be refreshed.
        
        Authentication Method: Verifies peer identities via Pre-Shared Keys (PSK) or digital certificates.
      - Operational Phases
        
        Phase 1 (IKE SA): Authenticates peers and builds a secure, encrypted management tunnel.
        
        Phase 2 (IPsec SA): Uses the IKE SA channel to negotiate specific parameters and keys to protect actual user data traffic.
    - - Core Components
        
        Supplicant: The client device (laptop, smartphone) trying to join the network.
        
        Authenticator: The gatekeeper device (wireless access point or network switch) that relays messages.
        
        Authentication Server: Usually a RADIUS server that verifies credentials and grants or denies access.
      - Common EAP Methods
        
        EAP-TLS: Uses digital certificates on both the client and server for high-security mutual authentication.
        
        PEAP (Protected EAP): Creates an encrypted TLS tunnel to safely transport inner password credentials like MSCHAPv2.
        
        EAP-FAST: Uses a protected access credential to achieve secure authentication without client certificates.
    - - How it works
        
        Detection: Peers check capabilities using hash values during initial IKE (Internet Key Exchange) handshakes on UDP port 500.
        
        Port Float: If a NAT router is found between the endpoints, both sides switch communication to UDP port 4500.
        
        Encapsulation: An extra 8-byte UDP header is inserted between the outer IP header and the inner ESP/IPsec payload.
        
        Keepalives: Periodic empty or non-data packets go out over port 4500 to keep the router's NAT translation mapping active.
      - Requirement
        
        UDP 500: Used for original IKE negotiation.
        
        UDP 4500: Used for NAT-T encapsulation and data transfer.
        
        IP Protocol 50 (ESP): Allowed if raw non-encapsulated tunnels are used alongside NAT-T.
    - - How it works
        
        Traffic-Based Checking: Instead of constantly sending dummy packets, DPD relies on regular data flow. If data is passing through the tunnel, the peer is assumed to be alive.
        
        Probing: When an IPsec connection goes idle and traffic needs to be sent, or when preset idle timers trigger, a lightweight probe (R-U-THERE in IKEv1, or empty informational requests in IKEv2 liveness checks) is sent to the remote peer.
        
        Acknowledgment: If the remote peer responds (R-U-THERE-ACK), the connection is verified.
        
        Failure Action: If no response is received after a configured number of retries and retry intervals, the local device tears down the dead security associations and triggers a re-negotiation or a failover to a backup route.
      - Benefit
        
        Efficiency: Avoids unnecessary bandwidth usage by staying quiet during active data transfer.
        
        Fast Recovery: Detects dropped connections much faster than waiting for standard crypto-key lifetimes to expire.
        
        Better Failover: Allows routing tables and high-availability clusters to switch over to backup paths rapidly.
    - - Common Groups and Sizes
        
        Group 1 & 2: 768-bit and 1024-bit (MODP) — Outdated and insecure; avoid using them.
        
        Group 5: 1536-bit (MODP) — Older standard, weak for modern high-level encryption.
        
        Group 14: 2048-bit (MODP) — Standard baseline; good for 128-bit encryption.
        
        Group 15 & 16: 3072-bit and 4096-bit (MODP) — Higher strength modular exponentiation.
        
        Group 19 & 20: 256-bit and 384-bit (ECP/Elliptic Curve) — Fast and strong using smaller key sizes.
        
        Group 21: 521-bit (ECP) — High-security elliptic curve for 256-bit encryption and above.
      - Selection Factors
        
        Compatibility: Both connecting devices must support and match the configured DH group during negotiation.
        
        Performance: Users on r/fortinet reach a consensus that Elliptic Curve groups (like 19, 20, and 21) are preferred for their speed and efficiency over older MODP numbers.