Is any method to decrypt LTM HealtMonitor from tcpdump that is using TLS1.2 and Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 ?
iRule is not an option, because HealtMonitor is not traversing virtual server and act as a client to node Server.
ssldump does not support ECDHE session keys.
Server side tcpdump is not an option.
Certificate and private key from server side are available.
the only way would be for the client (F5) or server (server) to output the session key.
for a health monitor im not aware of any way to make that happen, perhaps the server wants to?
my question is why? you can easily replicate the behaviour with a curl or openssl s_client from the big-ip, why does the health monitor traffic have to decrypted?