diff --git a/README-zh.md b/README-zh.md
index 16c5c41..328fe7b 100644
--- a/README-zh.md
+++ b/README-zh.md
@@ -138,9 +138,9 @@ DigitalOcean 用户可以参考这个<a href="https://usefulpcguide.com/17318/cr
 
 *其他语言版本: [English](README.md#important-notes), [简体中文](README-zh.md#重要提示).*
 
-**Windows 和 Android 用户**： 如果在连接过程中遇到错误，请参见 <a href="docs/clients-zh.md#故障排除" target="_blank">故障排除</a>。
+**Windows 用户** 在首次连接之前需要<a href="docs/clients-zh.md#windows-错误-809" target="_blank">修改一次注册表</a>，以解决 VPN 服务器 和/或 客户端与 NAT （比如家用路由器）的兼容问题。
 
-同一个 VPN 账户可以在你的多个设备上使用。但是由于 IPsec 的局限性，在同一个 NAT 后面（比如家用路由器）一次只能连接一个设备到 VPN 服务器。即使你创建多个用户也是如此。
+同一个 VPN 账户可以在你的多个设备上使用。但是由于 IPsec/L2TP 的局限性，如果你需要同时连接在同一个 NAT 后面（比如家用路由器）的多个设备到 VPN 服务器，你必须仅使用 <a href="docs/clients-xauth-zh.md" target="_blank">IPsec/XAuth 模式</a>。
 
 如果需要添加，修改或者删除 VPN 用户账户，请参见 <a href="docs/manage-users-zh.md" target="_blank">管理 VPN 用户</a>。
 
diff --git a/README.md b/README.md
index 6aac510..57228c2 100644
--- a/README.md
+++ b/README.md
@@ -138,9 +138,9 @@ Enjoy your very own VPN! :sparkles::tada::rocket::sparkles:
 
 *Read this in other languages: [English](README.md#important-notes), [简体中文](README-zh.md#重要提示).*
 
-**Windows and Android users**: If you get an error when trying to connect, see <a href="docs/clients.md#troubleshooting" target="_blank">Troubleshooting</a>.
+For **Windows users**, this <a href="docs/clients.md#windows-error-809" target="_blank">one-time registry change</a> is required if the VPN server and/or client is behind NAT (e.g. home router).
 
-The same VPN account can be used by your multiple devices. However, due to an IPsec limitation, only one device behind the same NAT (e.g. home router) can connect to the VPN server at a time. This applies even if you create multiple users.
+The same VPN account can be used by your multiple devices. However, due to an IPsec/L2TP limitation, you must use only <a href="docs/clients-xauth.md" target="_blank">IPsec/XAuth mode</a> if you wish to connect multiple devices simultaneously from behind the same NAT (e.g. home router).
 
 If you wish to add, edit or remove VPN user accounts, see <a href="docs/manage-users.md" target="_blank">Manage VPN Users</a>.
 
diff --git a/docs/clients-zh.md b/docs/clients-zh.md
index 7bf3dfc..6b7eebd 100644
--- a/docs/clients-zh.md
+++ b/docs/clients-zh.md
@@ -43,6 +43,8 @@
 1. 单击 **确定** 关闭 **高级设置**。
 1. 单击 **确定** 保存 VPN 连接的详细信息。
 
+注： 在首次连接之前需要修改一次注册表。请参见下面的说明。
+
 ### Windows 7, Vista and XP
 
 1. 单击开始菜单，选择控制面板。
@@ -69,6 +71,8 @@
 1. 单击 **确定** 关闭 **高级设置**。
 1. 单击 **确定** 保存 VPN 连接的详细信息。
 
+注： 在首次连接之前需要<a href="#windows-错误-809">修改一次注册表</a>，以解决 VPN 服务器 和/或 客户端与 NAT （比如家用路由器）的兼容问题。
+
 要连接到 VPN： 单击系统托盘中的无线/网络图标，选择新的 VPN 连接，然后单击 **连接**。如果出现提示，在登录窗口中输入 `你的 VPN 用户名` 和 `密码` ，并单击 **确定**。最后你可以到 <a href="https://www.ipchicken.com" target="_blank">这里</a> 检测你的 IP 地址，应该显示为`你的 VPN 服务器 IP`。
 
 如果在连接过程中遇到错误，请参见 <a href="#故障排除">故障排除</a>。
diff --git a/docs/clients.md b/docs/clients.md
index 68d2c77..aa020a2 100644
--- a/docs/clients.md
+++ b/docs/clients.md
@@ -43,6 +43,8 @@ An alternative <a href="https://usefulpcguide.com/17318/create-your-own-vpn/" ta
 1. Click **OK** to close the **Advanced settings**.
 1. Click **OK** to save the VPN connection details.
 
+Note: A one-time registry change is required before connecting. See details below.
+
 ### Windows 7, Vista and XP
 
 1. Click on the Start Menu and go to the Control Panel.
@@ -69,6 +71,8 @@ An alternative <a href="https://usefulpcguide.com/17318/create-your-own-vpn/" ta
 1. Click **OK** to close the **Advanced settings**.
 1. Click **OK** to save the VPN connection details.
 
+Note: This <a href="#windows-error-809">one-time registry change</a> is required if the VPN server and/or client is behind NAT (e.g. home router).
+
 To connect to the VPN: Click on the wireless/network icon in your system tray, select the new VPN entry, and click **Connect**. If prompted, enter `Your VPN Username` and `Password`, then click **OK**. You can verify that your traffic is being routed properly by <a href="https://encrypted.google.com/search?q=my+ip" target="_blank">looking up your IP address on Google</a>. It should say "Your public IP address is `Your VPN Server IP`".
 
 If you get an error when trying to connect, see <a href="#troubleshooting">Troubleshooting</a>.
diff --git a/docs/ikev2-howto-zh.md b/docs/ikev2-howto-zh.md
index dbb8865..481fb7a 100644
--- a/docs/ikev2-howto-zh.md
+++ b/docs/ikev2-howto-zh.md
@@ -15,7 +15,7 @@ Libreswan 支持通过使用 RSA 签名算法的 X.509 Machine Certificates 来
 - Windows 7, 8.x 和 10
 - Windows Phone 8.1 及以上
 - strongSwan Android VPN 客户端
-- <a href="https://github.com/gaomd/docker-ikev2-vpn-server">iOS (iPhone/iPad) 和 OS X (macOS)</a> <-- 请参见
+- <a href="https://github.com/gaomd/docker-ikev2-vpn-server" target="_blank">iOS (iPhone/iPad) 和 OS X (macOS)</a> <-- 请参见
 
 下面举例说明如何在 Libreswan 上配置 IKEv2。以下命令必须用 `root` 账户运行。
 
@@ -224,6 +224,8 @@ Libreswan 支持通过使用 RSA 签名算法的 X.509 Machine Certificates 来
 
    https://wiki.strongswan.org/projects/strongswan/wiki/Win7Connect
 
+   （可选步骤） 如需启用更安全的加密方式，可以添加 <a href="https://wiki.strongswan.org/projects/strongswan/wiki/Windows7#AES-256-CBC-and-MODP2048" target="_blank">这个注册表键</a> 并重启。
+
    #### Windows Phone 8.1 及以上
 
    首先导入 `.p12` 文件，然后参照 <a href="https://technet.microsoft.com/en-us/windows/dn673608.aspx" target="_blank">这些说明</a> 配置一个基于证书的 IKEv2 VPN。
diff --git a/docs/ikev2-howto.md b/docs/ikev2-howto.md
index d65e5f7..b2d9a15 100644
--- a/docs/ikev2-howto.md
+++ b/docs/ikev2-howto.md
@@ -15,7 +15,7 @@ Libreswan can authenticate IKEv2 clients on the basis of X.509 Machine Certifica
 - Windows 7, 8.x and 10
 - Windows Phone 8.1 and above
 - strongSwan Android VPN client
-- <a href="https://github.com/gaomd/docker-ikev2-vpn-server">iOS (iPhone/iPad) and OS X (macOS)</a> <-- See link
+- <a href="https://github.com/gaomd/docker-ikev2-vpn-server" target="_blank">iOS (iPhone/iPad) and OS X (macOS)</a> <-- See link
 
 The following example shows how to configure IKEv2 with Libreswan. Commands below must be run as `root`.
 
@@ -224,6 +224,8 @@ Before continuing, make sure you have successfully <a href="https://github.com/h
 
    https://wiki.strongswan.org/projects/strongswan/wiki/Win7Connect
 
+   (Optional) To enable stronger ciphers, you may add <a href="https://wiki.strongswan.org/projects/strongswan/wiki/Windows7#AES-256-CBC-and-MODP2048" target="_blank">this registry key</a> and reboot.
+
    #### Windows Phone 8.1 and above
 
    First import the `.p12` file, then follow <a href="https://technet.microsoft.com/en-us/windows/dn673608.aspx" target="_blank">these instructions</a> to configure a certificate-based IKEv2 VPN.