The ikev2 delete old child-sa enable command enables the function of instructing the peer device to delete the old child SA.
The undo ikev2 delete old child-sa enable command disables the function of instructing the peer device to delete the old child SA.
By default, the function of instructing the peer device to delete the old child SA is enabled.
In an IKEv2 scenario, when the local device deletes the child SA and initiates IKEv2 negotiation to the peer device again, the default negotiation message carries the IKEV2_NOTIFY_DELETE_OLD_CHILDSA payload, instructing the peer device to delete the old child SA. If the peer device does not support the processing of this payload, IKEv2 negotiation between the two ends fails. To prevent this problem, run the undo ikev2 delete old child-sa enable command on the local device to disable it from instructing the peer device to delete the old child SA so that the IKEv2 negotiation message does not carry this payload.