diff --git a/trunk/conf/full.conf b/trunk/conf/full.conf
index b53766ef2..809eb1cb2 100644
--- a/trunk/conf/full.conf
+++ b/trunk/conf/full.conf
@@ -412,7 +412,7 @@ rtc_server {
     # The exposed candidate IPs, response in SDP candidate line. It can be:
     #       *           Retrieve server IP automatically, from all network interfaces.
     #       eth0        Retrieve server IP by specified network interface name. # TODO: Implements it.
-    #       $CANDIDATE  Read the IP from ENV variable $EIP, use * if not set, see https://github.com/ossrs/srs/issues/307#issuecomment-599028124
+    #       $CANDIDATE  Read the IP from ENV variable, use * if not set, see https://github.com/ossrs/srs/issues/307#issuecomment-599028124
     #       x.x.x.x     A specified IP address or DNS name, which can be access by client such as Chrome.
     # You can specific more than one interface name:
     #       eth0 eth1   Use network interface eth0 and eth1. # TODO: Implements it.
diff --git a/trunk/conf/rtc.conf b/trunk/conf/rtc.conf
index 608ba3798..f628813d9 100644
--- a/trunk/conf/rtc.conf
+++ b/trunk/conf/rtc.conf
@@ -28,6 +28,7 @@ rtc_server {
     # The * means retrieving server IP automatically, from all network interfaces,
     # @see https://github.com/ossrs/srs/issues/307#issuecomment-599028124
     candidate       $CANDIDATE;
+    #candidate 10.0.0.123;
 }
 
 vhost __defaultVhost__ {
diff --git a/trunk/src/app/srs_app_rtc_server.cpp b/trunk/src/app/srs_app_rtc_server.cpp
index a44d82e7b..2704833dd 100644
--- a/trunk/src/app/srs_app_rtc_server.cpp
+++ b/trunk/src/app/srs_app_rtc_server.cpp
@@ -39,6 +39,7 @@
 #include <srs_service_utility.hpp>
 #include <srs_app_rtc_source.hpp>
 #include <srs_app_rtc_api.hpp>
+#include <srs_protocol_utility.hpp>
 
 // @global dtls certficate for rtc module.
 SrsDtlsCertificate* _srs_rtc_dtls_certificate = new SrsDtlsCertificate();
@@ -331,11 +332,13 @@ srs_error_t SrsRtcServer::create_session(
     // We allows to mock the eip of server.
     if (!mock_eip.empty()) {
         local_sdp.add_candidate(mock_eip, _srs_config->get_rtc_server_listen(), "host");
+        srs_trace("RTC: Use candidate mock_eip %s", mock_eip.c_str());
     } else {
         std::vector<string> candidate_ips = get_candidate_ips();
         for (int i = 0; i < (int)candidate_ips.size(); ++i) {
             local_sdp.add_candidate(candidate_ips[i], _srs_config->get_rtc_server_listen(), "host");
         }
+        srs_trace("RTC: Use candidates %s", srs_join_vector_string(candidate_ips, ", ").c_str());
     }
 
     SrsRtcSession* session = new SrsRtcSession(this);
@@ -357,7 +360,7 @@ srs_error_t SrsRtcServer::create_session(
     return err;
 }
 
-srs_error_t SrsRtcServer::create_session2(SrsSdp& local_sdp, SrsRtcSession** psession)
+srs_error_t SrsRtcServer::create_session2(SrsSdp& local_sdp, const std::string& mock_eip, SrsRtcSession** psession)
 {
     srs_error_t err = srs_success;
 
@@ -374,9 +377,15 @@ srs_error_t SrsRtcServer::create_session2(SrsSdp& local_sdp, SrsRtcSession** pse
     local_sdp.set_fingerprint(_srs_rtc_dtls_certificate->get_fingerprint());
 
     // We allows to mock the eip of server.
-    std::vector<string> candidate_ips = get_candidate_ips();
-    for (int i = 0; i < (int)candidate_ips.size(); ++i) {
-        local_sdp.add_candidate(candidate_ips[i], _srs_config->get_rtc_server_listen(), "host");
+    if (!mock_eip.empty()) {
+        local_sdp.add_candidate(mock_eip, _srs_config->get_rtc_server_listen(), "host");
+        srs_trace("RTC: Use candidate mock_eip %s", mock_eip.c_str());
+    } else {
+        std::vector<string> candidate_ips = get_candidate_ips();
+        for (int i = 0; i < (int)candidate_ips.size(); ++i) {
+            local_sdp.add_candidate(candidate_ips[i], _srs_config->get_rtc_server_listen(), "host");
+        }
+        srs_trace("RTC: Use candidates %s", srs_join_vector_string(candidate_ips, ", ").c_str());
     }
 
     session->set_local_sdp(local_sdp);
diff --git a/trunk/src/app/srs_app_rtc_server.hpp b/trunk/src/app/srs_app_rtc_server.hpp
index 164971710..84aeb4128 100644
--- a/trunk/src/app/srs_app_rtc_server.hpp
+++ b/trunk/src/app/srs_app_rtc_server.hpp
@@ -81,7 +81,7 @@ public:
         SrsRtcSession** psession
     );
     // We start offering, create_session2 to generate offer, setup_session2 to handle answer.
-    srs_error_t create_session2(SrsSdp& local_sdp, SrsRtcSession** psession);
+    srs_error_t create_session2(SrsSdp& local_sdp, const std::string& mock_eip, SrsRtcSession** psession);
     srs_error_t setup_session2(SrsRtcSession* session, SrsRequest* req, const SrsSdp& remote_sdp);
     // Destroy the session from server.
     void destroy(SrsRtcSession* session);