Why Identity fields are encrypted in IPsec phase 1 around packet 5/6 ? provided that the Identity field contains IP of either end. Does it has any significance ? Does it holds anything different then any end firewall IP?
Even if the identities equal the IP addresses there might be an added benefit to encrypting them, as a passive attacker won't see that that's the case. Because the identities could be different than the IP address of the endpoints (e.g. a FQDN or a Distinguished Name of a certificate).