ssh-agentを使ってsshのパスフレーズを省略する方法

fuka@techo:~$ ssh xsrv    #←接続１回目
Enter passphrase for key '/home/fuka/.ssh/****.xserver.jp.pem':
Last login: Mon Jan 30 10:07:36 2017 from *****.ne.jp
[ygkb@sv1507 ~]$ exit
logout
Connection to ****.xserver.jp closed.

fuka@techo:~$ ssh xsrv    #←接続２回目
Enter passphrase for key '/home/fuka/.ssh/****.xserver.jp.pem':    #←また入力。面倒くさい
Last login: Tue Jan 31 23:04:21 2017 from *****.ne.jp
：（略）

eval `ssh-agent`

ssh-add

fuka@techo:~$ ssh-add
Enter passphrase for /home/fuka/.ssh/id_rsa:
Identity added: /home/fuka/.ssh/id_rsa (/home/fuka/.ssh/id_rsa)

fuka@techo:~$ ssh-add ~/.ssh/file-a.pem ~/.ssh/file-b.pem
Enter passphrase for /home/fuka/.ssh/file-a.pem:
Identity added: /home/fuka/.ssh/id_rsa (/home/fuka/.ssh/file-a.pem)
Enter passphrase for /home/fuka/.ssh/file-b.pem:
Identity added: /home/fuka/.ssh/id_rsa (/home/fuka/.ssh/file-b.pem)

fuka@techo:~$ ssh-add    #パスフレーズ登録
Enter passphrase for /home/fuka/.ssh/id_rsa:
Identity added: /home/fuka/.ssh/id_rsa (/home/fuka/.ssh/id_rsa)
fuka@techo:~$ ssh xsrv    #SSH接続
Last login: Tue Jan 31 23:04:35 2017 from *****.vectant.ne.jp    #←スルーパス
[ygkb@sv1507 ~]$