接続時のログはどうなってますか?
正常に接続している僕の環境のログはこんな↓です。
---最初はIKE(共有シークレットのキー交換)認証
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: receive success. (Responder, Main-Mode message 1).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: transmit success. (Responder, Main-Mode message 2).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: receive success. (Responder, Main-Mode message 3).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: transmit success. (Responder, Main-Mode message 4).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKEv1 Phase1 AUTH: success. (Responder, Main-Mode Message 5).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: receive success. (Responder, Main-Mode message 5).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKEv1 Phase1 Responder: success. (Responder, Main-Mode).
Jan 30 14:14:52 (サーバ名) racoon[139]: IKE Packet: transmit success. (Responder, Main-Mode message 6).
Jan 30 14:14:53 (サーバ名) racoon[139]: Connecting.
Jan 30 14:14:53 (サーバ名) racoon[139]: IKE Packet: receive success. (Responder, Quick-Mode message 1).
Jan 30 14:14:53 (サーバ名) racoon[139]: IKE Packet: transmit success. (Responder, Quick-Mode message 2).
Jan 30 14:14:53 (サーバ名) racoon[139]: IKE Packet: receive success. (Responder, Quick-Mode message 3).
Jan 30 14:14:53 (サーバ名) racoon[139]: IKEv1 Phase2 Responder: success. (Responder, Quick-Mode).
Jan 30 14:14:53 (サーバ名) racoon[139]: Connected.---キー交換完了
---ここから本番のVPN接続
Jan 30 14:14:53 (サーバ名) vpnd[73]: Incoming call... Address given to client = 192.168.0.224
Jan 30 14:14:53 (サーバ名) com.apple.ppp.l2tp[73]: 2012-01-30 14:14:53 JST Incoming call... Address given to client = 192.168.0.224 ---配布するローカルIPアドレス
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53: --- last message repeated 1 time ---
Jan 30 14:14:53 (サーバ名) pppd[62265]: pppd 2.4.2 (Apple version 412.5) started by root, uid 0
Jan 30 14:14:53 (サーバ名) pppd[62265]: L2TP incoming call in progress from '接続するPCのIPアドレス'...
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53 (サーバ名) pppd[62265]: L2TP connection established.
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53 (サーバ名) pppd[62265]: Connect: ppp0 <--> socket[34:18]
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53: --- last message repeated 9 times ---
Jan 30 14:14:53 (サーバ名) pppd[62265]: CHAP peer authentication succeeded for ユーザ名
Jan 30 14:14:53 (サーバ名) pppd[62265]: DSAccessControl plugin: User 'ユーザ名' authorized for access
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53: --- last message repeated 1 time ---
Jan 30 14:14:53 (サーバ名) pppd[62265]: Unsupported protocol 0x8057 received
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53 (サーバ名) pppd[62265]: local IP address VPNサーバIPのアドレス
Jan 30 14:14:53 (サーバ名) pppd[62265]: remote IP address 192.168.0.224
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53 (サーバ名) pppd[62265]: l2tp_wait_input: Address added. previous interface setting (name: en0, address: VPNサーバIPのアドレス), current interface setting (name: ppp0, family: PPP, address: VPNサーバIPのアドレス, subnet: 255.255.255.0, destination: 192.168.0.224).
Jan 30 14:14:53 (サーバ名) /usr/sbin/serialnumberd[934]: Responding to network change notification.
Jan 30 14:14:53 (サーバ名) configd[32]: network configuration changed.