This INTEGER (none, ipv4, distinguishedName, fqdn) is described as the type of the Local IKE Identity for this crypto map entry, which the description says must be set together with the actual identity value object. An admin selects the type so the device tells its peer how to interpret the paired identity string, whether as a raw IPv4 address, a certificate distinguished name, or a fully qualified domain name. For example, an admin identifying a gateway by hostname rather than its NAT-translated address would set this to 'fqdn' to match a local identity value like 'gw1.example.com'.