Fixing SSH login slow issue

on the new VBox nodes,  ssh access is slow.

trace:
debug2: key: /root/.ssh/id_dsa ((nil)),
debug2: key: /root/.ssh/id_ecdsa ((nil)),
…
….Slow here…
…
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password
debug3: preferred publickey,keyboard-interactive,password

To Solve the problem, I can see the Box with public network access can reply soon,
Its the reverse ip DNS issue,

Solve:
On Server side: sshd_config

Link:
Fixing SSH login long delay