Could the two be used together? For ex. one side of asa configured with ike/ike2 and other with isakmp

Shark AttackNetwork adminAsked:
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btanExec ConsultantCommented:
To clarify to be on same understanding, IKE is also known as ISAKMP. IPsec-based VPN technologies use the ISAKMP and IPsec tunneling standards to build and manage tunnels. IKE is the key management protocol used to authenticate IPsec peers, negotiate and distribute IPsec encryption keys, and to automatically establish IPsec security associations (SAs). They are the same.

For IKEv1 and IKEv2, ASA supports both. ASA introduced support for IPSEC IKEv2 in software version 8.4(1) and later. Legacy IKEv1 is still supported. See these are point to make sure both end can negotiate and confirm the actual SA to transact via the agreed tunnel to be built
When you configure IKE on a device that supports IKEv2, you have the option of configuring either version alone, or both versions together. When the device attempts to negotiate a connection with another peer, it uses whichever versions you allow and that the other peer accepts. If you allow both versions, the device automatically falls back to the other version if negotiations are unsuccessful with the initially chosen version (IKEv2 is always tried first if it is configured). Both peers must support IKEv2 to use it in a negotiation.

With IKEv1 policies, for each parameter, you set one value. For IKEv2, you can configure multiple encryption, integrity, PRF, and Diffie-Hellman options. The ASA orders the settings from the most secure to the least secure and negotiates with the peer using that order. This allows you to potentially send a single proposal to convey all the allowed transforms instead of the need to send each allowed combination as with IKEv1.

If you select AES encryption, to support the large key sizes required by AES, ISAKMP negotiation should use Diffie-Hellman (DH) Group 5 or higher. ASA devices support groups 1, 2, and 5 only, and these are the only groups available for IKEv2.
Shark AttackNetwork adminAuthor Commented:
so in other words, i should be OK. One asa i have is an older device 5520 running 8.2 and i can only configure with isakmp i do not have an option for ike and an the other asa which is 5506, you can only configure it with ike.
btanExec ConsultantCommented:
yes they will need to negotiate as long as the asa setting are set to support both or IKEv1 minimally only. For older version (not avail option to config) it is restricted to only IKEv1 so the other end will use it to further comms to complete in build the common SA.

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