1、网络地址转换 2、路由 3、OSI模型 4、网络层 5、集线器，交换机和路由器解释 - 有什么区别？ 6、https://openvpn.net/community-resources/how-to/#determining-whether-to-use-a-routed-or-bridged-vpn Setting up a VPN often entails linking together private subnets from different locations. The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets (codified in RFC 1918): 
While addresses from these netblocks should normally be used in VPN configurations, it’s important to select addresses that minimize the probability of IP address or subnet conflicts. The types of conflicts that need to be avoided are:
- conflicts from different sites on the VPN using the same LAN subnet numbering, or
- remote access connections from sites which are using private subnets which conflict with your VPN subnets.
7、What is a subnet? 
子网网址选择注意：（摘自 https://routersecurity.org/ipaddresses.php）
- If you prefer 192.168, then avoid networks where the third number is 0, 1, 2, 3 (Amped Wireless, Huawei), 4 (Zoom), 5 (used by Hawking), 7 (Eero), 8 (used by GLi and Huawei), 9 (Gryphon), 10 (Motorola,NetComm), 11 (Buffalo), 15 (D-Link, Linksys), 16 (Linksys), 19 (Anonabox), 20 (Motorola,NetComm), 30 (Motorola), 50 (Peplink), 55 (Luma), 62 (Motorola), 72 (Asus Lyra), 85 and 86 ( Google), 88 (used by MikroTik), 100 (used by assorted cable modems and Huawei), 102 (Motorola), 123 (LevelOne, Sitecom), 168 (Sonicwall), 178 (used by FRITZ!Box), 218 (Firewalla), 223 (Trendnet), and 254 (D-Link, Actiontec).
- If you prefer IP addresses starting with 10, then the subnets to avoid are 10.0.0.x (Netgear, Asus, Cisco, 2Wire, etc), 10.0.1.x (Apple), 10.1.1.x (Belkin, D-Link), 10.1.10.x (SMC), 10.10.1.x (Asus), 10.10.10.x (used by HooToo in their HT-TM05 TripMate Titan Wi-Fi sharing device) and 10.90.90.x (D-Link). Some easy to remember networks would be 10.11.12.x and 10.20.30.x. That said, easy to remember should not be a priority, security should be. So, something that no one would guess, like 10.43.27.x is better. If you live at 123 Main Street, then 10.123.123.x is a great choice.
8、http://jodies.de/ipcalc?host=10.0.0.0&mask1=24 
9、域名系统 域名系统（英语：Domain Name System，缩写：DNS）是互联网的一项服务。它作为将域名和IP地址相互映射的一个分布式数据库，能够使人更方便地访问互联网。DNS使用TCP和UDP端口53。当前，对于每一级域名长度的限制是63个字符，域名总长度则不能超过253个字符。
10、https://www.draytek.com/support/knowledge-base/5452 
