Hi Alan, Thank you so much. when i set one client server to my radius server ,the vpn users work fine. but while there are two client servers ,the second client cant connect the radius server. radius server : client.conf -------------- client [vpn1-IP]{ secret = secret1 nastype = other } client [vpn2-IP]{ secret = secret2 nastype = other } ------------- radius.log ------------- Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Connected new DB handle, #0 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Attempting to connect rlm_sql_mysql #1 Wed Sep 17 04:07:16 2014 : Info: rlm_sql_mysql: Starting connect to MySQL server for #1 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Connected new DB handle, #1 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Attempting to connect rlm_sql_mysql #2 Wed Sep 17 04:07:16 2014 : Info: rlm_sql_mysql: Starting connect to MySQL server for #2 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Connected new DB handle, #2 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Attempting to connect rlm_sql_mysql #3 Wed Sep 17 04:07:16 2014 : Info: rlm_sql_mysql: Starting connect to MySQL server for #3 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Connected new DB handle, #3 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Attempting to connect rlm_sql_mysql #4 Wed Sep 17 04:07:16 2014 : Info: rlm_sql_mysql: Starting connect to MySQL server for #4 Wed Sep 17 04:07:16 2014 : Info: rlm_sql (sql): Connected new DB handle, #4 Wed Sep 17 04:07:16 2014 : Info: Loaded virtual server <default> Wed Sep 17 04:07:16 2014 : Info: Loaded virtual server inner-tunnel Wed Sep 17 04:07:16 2014 : Info: ... adding new socket proxy address * port 54648 Wed Sep 17 04:07:16 2014 : Info: Ready to process requests. Wed Sep 17 04:18:23 2014 : Error: Ignoring request to authentication address * port 1812 from unknown client [IP address] port 47118 Wed Sep 17 04:18:33 2014 : Error: Ignoring request to authentication address * port 1812 from unknown client [IP address] port 47118 Wed Sep 17 04:18:43 2014 : Error: Ignoring request to authentication address * port 1812 from unknown client [IP address] port 47118 ------------- the second client server log ----------- Sep 17 04:18:19 vpn2 pppd[8096]: pppd 2.4.5 started by root, uid 0 Sep 17 04:18:19 vpn2 pppd[8096]: Using interface ppp0 Sep 17 04:18:19 vpn2 pppd[8096]: Connect: ppp0 <--> /dev/pts/1 Sep 17 04:18:53 vpn2 pppd[8096]: rc_ip_hostname: couldn't look up host by addr: %lX Sep 17 04:18:53 vpn2 pppd[8096]: rc_send_server: no reply from RADIUS server unknown:1812 Sep 17 04:18:53 vpn2 pppd[8096]: Peer vpn2test01 failed CHAP authentication Sep 17 04:18:53 vpn2 pppd[8096]: Modem hangup Sep 17 04:18:53 vpn2 pppd[8096]: Connection terminated. Sep 17 04:18:53 vpn2 pppd[8096]: Exit. ------------------ If there is only vpn1 client, the client server and radius all ok ,while two , the vpn1 still wor fine, but the vpn2 is not. Why the radius server cant make response to the vpn2 client server? Thanks.