diff --git a/man/shadowsocks-libev.8 b/man/shadowsocks-libev.8
index 2b448354..fcbd6192 100644
--- a/man/shadowsocks-libev.8
+++ b/man/shadowsocks-libev.8
@@ -104,7 +104,13 @@ Not available in manager mode.
 Only available on Linux.
 .TP
 .B \-i \fIinterface\fP
-Specify network interface to bind.
+Send traffic through specific network interface.
+
+For example, there are three interfaces in your device, which is lo (127.0.0.1),
+eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure
+\fBshadowsocks-libev\fR to listen on 0.0.0.0:8388 and bind to eth1. That results
+the traffic go out through eth1, but not lo nor eth0. This option is useful to
+control traffic in multi-interface environment.
 
 Not available in redir mode.
 .TP
diff --git a/man/ss-local.1 b/man/ss-local.1
index 9a35d7c3..ee9c0223 100644
--- a/man/ss-local.1
+++ b/man/ss-local.1
@@ -89,7 +89,13 @@ Specify max number of open files.
 Only avaliable on Linux.
 .TP
 .B \-i \fIinterface\fP
-Specify network interface to bind.
+Send traffic through specific network interface.
+
+For example, there are three interfaces in your device, which is lo (127.0.0.1),
+eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure \*(Lo to
+listen on 0.0.0.0:8388 and bind to eth1. That results the traffic go out through
+eth1, but not lo nor eth0. This option is useful to control traffic in
+multi-interface environment.
 .TP
 .B \-b \fIlocal_address\fP
 Specify local address to bind.
diff --git a/man/ss-manager.1 b/man/ss-manager.1
index cab021a8..51e2c1d2 100644
--- a/man/ss-manager.1
+++ b/man/ss-manager.1
@@ -83,7 +83,13 @@ Set the socket timeout in seconds. The default value is 60.
 Use a configuration file.
 .TP
 .B \-i \fIinterface\fP
-Specify network interface to bind.
+Send traffic through specific network interface.
+
+For example, there are three interfaces in your device, which is lo (127.0.0.1),
+eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure \*(Ma to
+listen on 0.0.0.0:8388 and bind to eth1. That results the traffic go out through
+eth1, but not lo nor eth0. This option is useful to control traffic in
+multi-interface environment.
 .TP
 .B \-u
 Enable UDP relay.
diff --git a/man/ss-server.1 b/man/ss-server.1
index 6b952640..5f4223c0 100644
--- a/man/ss-server.1
+++ b/man/ss-server.1
@@ -88,7 +88,13 @@ Specify max number of open files.
 Only avaliable on Linux.
 .TP
 .B \-i \fIinterface\fP
-Specify network interface to bind.
+Send traffic through specific network interface.
+
+For example, there are three interfaces in your device, which is lo (127.0.0.1),
+eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure \*(Se to
+listen on 0.0.0.0:8388 and bind to eth1. That results the traffic go out through
+eth1, but not lo nor eth0. This option is useful to control traffic in
+multi-interface environment.
 .TP
 .B \-u
 Enable UDP relay.
diff --git a/man/ss-tunnel.1 b/man/ss-tunnel.1
index 72e4997b..483f8af7 100644
--- a/man/ss-tunnel.1
+++ b/man/ss-tunnel.1
@@ -90,7 +90,13 @@ Specify max number of open files.
 Only avaliable on Linux.
 .TP
 .B \-i \fIinterface\fP
-Specify network interface to bind.
+Send traffic through specific network interface.
+
+For example, there are three interfaces in your device, which is lo (127.0.0.1),
+eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure \*(Tu to
+listen on 0.0.0.0:8388 and bind to eth1. That results the traffic go out through
+eth1, but not lo nor eth0. This option is useful to control traffic in
+multi-interface environment.
 .TP
 .B \-b \fIlocal_address\fP
 Specify local address to bind.