portal 无法重定向问题

在于其它厂商认证服务器做portal对接事，终端获取地址后无法弹出portal页面，手动输入页面地址可以认证。
debug 日志如下：

AC上配置方法如下：

# wlan service-template 1
 ssid WiFi_TSET
 client forwarding-location ap
 bss transition-management enable
 portal enable method direct
 portal domain Student
 portal bas-ip 10.100.255.11
 portal apply web-server AAA
 portal apply mac-trigger-server test
 service-template enable
 #                     
 radius scheme Student
 primary authentication 172.31.31.5
 primary accounting 172.31.31.5
 key authentication simple h3c7521340
 key accounting simple h3c7521340
 user-name-format without-domain
 nas-ip 10.100.255.11
 #                                     

radius session-control enable
 #
 domain Student
 authorization-attribute idle-cut 30 10240
 authentication portal radius-scheme Student
 authorization portal radius-scheme Student
 accounting portal radius-scheme Student   
#

portal server test
 ip 172.31.31.5 key simple XXX 
 server-type cmcc                       
#

portal web-server AAA
 url http://172.31.31.5
 url-parameter ssid ssid
 url-parameter wlanuserip source-address
 url-parameter wlanacname value AC
 server-type cmcc                         
#

portal free-rule 0 source ip any destination ip 144.144.144.144 255.255.255.255
 portal free-rule 5 source ip any destination ip any   
#

portal roaming enable
#

undo portal refresh arp enable