IPsec Negotiation Steps:
Phase 1 (ISAKMP Tunnel): Both peers authenticate and agree on security policies.
Phase 2 (IPsec Tunnel): Establishes encryption and integrity policies for data traffic.
Interesting Traffic: VPN negotiation is triggered by traffic that matches the defined ACL.
Configure ISAKMP Policy for IKE Phase 1:
Defines parameters such as encryption, hash, and authentication methods.
Configure IPsec Policy for Phase 2:
Specifies the protocols (ESP), encryption algorithms, and key exchange mechanisms.
Crypto Map:
Binds ACL, IPsec policies, and defines the peer address.
Apply IPsec Policy:
Apply the policy to the outbound interface and verify with the show crypto map command.
show crypto map
The ISAKMP policy defines the security associations (SAs) used to establish the tunnel.
Key Elements (HAGLE):
H: Hash (SHA)
A: Authentication (pre-shared key)
G: Group (Diffie-Hellman group 5
L: Lifetime (3600 seconds)
E: Encryption (AES)
Binding ACLs: Define traffic that will trigger the tunnel setup (interesting traffic).
Configure Peer Address and IPsec Parameters:
Include peer’s IP, DH group, and tunnel lifetime.
Verify the configuration using show crypto map.
Use show crypto isakmp sa and show crypto ipsec sa to verify the status of ISAKMP and IPsec tunnels.
show crypto isakmp sa
show crypto ipsec sa
Ping Test: Send traffic that matches the ACLs to verify the VPN tunnel is operational.
If multicast or broadcast traffic (like OSPF or EIGRP) needs to be routed through the tunnel, consider implementing a GRE tunnel for encapsulation.