router-a与router-b之间采用预共享密钥“12345678”建立IPSec关联，请完成下面配置。router-a(config)#cryptike key 1234567 8 address
router-a (config)#crypt ike key 12345678 address (5)
router-b (config)#crypt ike key 12345678 address (6)