N(REKEY_SA) is a payload used to indicate that it is not a new IPSEC_SA Creation activity but a Rekeying activity. Nonce is a random number which is used to provide uniqueness to a message. IKE_SA Rekeying message: CREATE_CHILD_SA Rekeying can be triggered in two scenarios :Ģ) After a predefined number of 'packets' have passed through the Secure channel ( IKE_SA / IPSEC_SA )įor rekeying, as mentioned in Part 2, CREATE_CHILD_SA exchanges are used. Both are independent in IKEv2 and won't affect the other one, i.e, when Communication Officer A and Communication Officer B channel is refreshed, Manager A and Manager B channel can be used as normal and vice versa. The reason is that a dedicated thief or hacker can eventually find our secret keys by some method and can steal the confidential information ( methods used are out of scope for this article ).Ĭonsidering our example of Part 1, the secure channel between Communication Officer A and Communication Officer B can be refreshed ( refreshing IKE_SA ) or the secure channel between Manager A and Manager B can be refreshed ( refreshing IPSEC_SA / CHILD_SA ). Now the question can arise as to why we need a 'refreshing' a.k.a fresh negotiation of keys after Secure channel is established successfully once. As mentioned above, by refreshing what we mean is a fresh negotiation for keys between the Initiator and Responder ( Communication Officer A and B or Manager A and B ). When a IKE_SA or CHILD_SA is established ( i.e, the secure communication channel between Communication Officer A and B or Manager A and B discussed in Part 1) we can determine how long the Secure channel between Communication Officer A and B or Manager A and Manager B should last before 'refreshing'. We can consider it as a kind of 'refreshment' activity. Rekeying, as the name suggests, represents generating a new set of keys. We will also touch upon Encapsulated Security Payload and How to Decrypt ISAKMP and ESP packets in wireshark. In this article we will discuss about certain important IPSec functionalities like Rekeying, Reauthentication, Dead Peer Detection and Common Errors Encountered while trying to establishing the IKE_SA and IPSEC_SA. Please read Part 1 and Part 2 without fail before proceeding as the examples and points discussed in Part 1 and Part 2 are used at several places in this article.

In Part 1 and Part 2 we discussed about Generic concepts of Tunnel and IKEv2 Messaging.

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