diff --git a/README-zh.md b/README-zh.md
index dec5b7d..7b993c1 100644
--- a/README-zh.md
+++ b/README-zh.md
@@ -159,7 +159,7 @@ sh vpnsetup.sh
 
 对于有外部防火墙的服务器（比如 <a href="https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-security-groups.html" target="_blank">EC2</a>/<a href="https://cloud.google.com/vpc/docs/firewalls" target="_blank">GCE</a>），请为 VPN 打开 UDP 端口 500 和 4500。阿里云用户请参见 [#433](https://github.com/hwdsl2/setup-ipsec-vpn/issues/433)。
 
-在 VPN 已连接时，客户端配置为使用 <a href="https://developers.google.com/speed/public-dns/" target="_blank">Google Public DNS</a>。如果偏好其它的域名解析服务，编辑 `/etc/ppp/options.xl2tpd` 和 `/etc/ipsec.conf` 并替换 `8.8.8.8` 和 `8.8.4.4`，然后重启服务器。
+在 VPN 已连接时，客户端配置为使用 <a href="https://developers.google.com/speed/public-dns/" target="_blank">Google Public DNS</a>。如果偏好其它的域名解析服务，编辑 `/etc/ppp/options.xl2tpd` 和 `/etc/ipsec.conf` 并替换 `8.8.8.8` 和 `8.8.4.4`，然后重启服务器。高级用户可以在运行 VPN 脚本时定义 `VPN_DNS_SRV1` 和 `VPN_DNS_SRV2`（可选）。
 
 使用内核支持有助于提高 IPsec/L2TP 性能。它在以下系统上可用： Ubuntu 16.04-20.04, Debian 9-10 和 CentOS 6-8. Ubuntu 系统需要安装 `linux-modules-extra-$(uname -r)`（或者 `linux-image-extra`），然后运行 `service xl2tpd restart`。
 
diff --git a/README.md b/README.md
index 12add58..cb03ef9 100644
--- a/README.md
+++ b/README.md
@@ -159,7 +159,7 @@ If you wish to add, edit or remove VPN user accounts, see <a href="docs/manage-u
 
 For servers with an external firewall (e.g. <a href="https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-security-groups.html" target="_blank">EC2</a>/<a href="https://cloud.google.com/vpc/docs/firewalls" target="_blank">GCE</a>), open UDP ports 500 and 4500 for the VPN. Aliyun users, see [#433](https://github.com/hwdsl2/setup-ipsec-vpn/issues/433).
 
-Clients are set to use <a href="https://developers.google.com/speed/public-dns/" target="_blank">Google Public DNS</a> when the VPN is active. If another DNS provider is preferred, replace `8.8.8.8` and `8.8.4.4` in both `/etc/ppp/options.xl2tpd` and `/etc/ipsec.conf`, then reboot your server.
+Clients are set to use <a href="https://developers.google.com/speed/public-dns/" target="_blank">Google Public DNS</a> when the VPN is active. If another DNS provider is preferred, replace `8.8.8.8` and `8.8.4.4` in both `/etc/ppp/options.xl2tpd` and `/etc/ipsec.conf`, then reboot your server. Advanced users can define `VPN_DNS_SRV1` and optionally `VPN_DNS_SRV2` when running the VPN setup script.
 
 Using kernel support could improve IPsec/L2TP performance. It is available on Ubuntu 16.04-20.04, Debian 9-10 and CentOS 6-8. Ubuntu users: Install `linux-modules-extra-$(uname -r)` (or `linux-image-extra`), then run `service xl2tpd restart`.