Hi, All I met same problem when compile kamailio with STUN support. http://www.voipuser.org/forum_topic_18741.html /usr/include/bits/string3.h:83: warning: memset used with constant zero length parameter; this could be due to transposed parameters ser_stun.o: In function `add_fingerprint': /root/kamailio-3.0.1/ser_stun.c:890: undefined reference to `SHA1' ser_stun.o: In function `validate_fingerprint': /root/kamailio-3.0.1/ser_stun.c:973: undefined reference to `SHA1' collect2: ld returned 1 exit status make: *** [kamailio] Error 1 I search online that need link libssl -lssl But I don't know where to add this compile flag. The Makefile of this project is too complicated for me to understand. Any one can tell me how to I can fix this? By the way, I have install libssl. It's /usr/lib/libssl.so.0.9.8 Sincerely, Derrick