使用SSH 登录 Ubnt，然后执行如下指令，将对应的参数修改成你自己的即可。
configure
set service dns dynamic interface pppoe1 service custom-pubyun host-name 3322域名
set service dns dynamic interface pppoe1 service custom-pubyun login 3322账号
set service dns dynamic interface pppoe1 service custom-pubyun options ssl=no
set service dns dynamic interface pppoe1 service custom-pubyun password 3322密码
set service dns dynamic interface pppoe1 service custom-pubyun protocol dyndns2
set service dns dynamic interface pppoe1 service custom-pubyun server www.pubyun.com
commit
save