IPsec Explained: How It Works and What to Look For
IPsec supplies security services at the IP layer using security associations.
Published by Protocol Explorer · Reviewed
How IPsec works
Peers apply policy and establish security associations; ESP can provide confidentiality and integrity for protected traffic. Key management is commonly handled by IKE.
What to look for in an exchange
Transport mode and tunnel mode protect different portions of the original packet. The security association identifies parameters and keys used for a direction of traffic.
Follow an example step by step
- Determine whether the example uses transport mode or tunnel mode.
- Identify the security association and ESP-protected traffic where visible.
- At an authorized endpoint, compare the protected inner traffic with the outer IP packet.
Common interpretation mistake
IPsec is a set of IP-layer security mechanisms, not one fixed handshake.
Key point to remember
IKE is commonly used to negotiate keys and security associations, but it is specified separately.
Explore the protocol
The IPsec overview is free without an account. Its full interactive lesson is included in Protocol Explorer Pro, a one-time $4.99 purchase; an account is required to buy Pro and restore the licence across devices.
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Specification
Read the primary specification for IPsec for the authoritative protocol details. The interactive scenario is a simplified teaching model, not a capture of your network.
Continue learning
How to read a packet · TCP · UDP · HTTPS