Every rekeying IPsec device generates a new Diffie-Hellman (DH) pair and new IPsec security association pairs for each peer
with which it is communicating. The new security association pairs are generated as a combination of the new DH private key
and the DH public key of each peer. The IPsec device distributes the new DH public value to the controller, which forwards
it to its authorized peers. Each peer continues to transmit to the existing security association, and subsequently, to new
security associations.
During a simultaneous rekey, up to four pairs of IPsec Security Associations (SAs) can be temporarily created. These four
pairs converge on a single rekey of a device.
An IPsec device can initiate a rekey due to reasons such as the local time or a volume-based policy, or the counter result
of a cipher counter mode initialization vector nearing completion.
When you configure a rekey on a local inbound security association, it triggers a peer outbound and inbound security association
rekey. The local outbound security association rekey is initiated after the IPsec device receives the first packet with the
new Security Parameter Index (SPI) from a peer.
Note
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A pairwise-key device can form IPsec sessions with both pairwise and nonpairwise devices.
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The rekeying process requires higher control plane CPU usage, resulting in lower session scaling.
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