【文章标题】：Falsehoods Programmers Believe About LANs
【文章标题】：程序员对局域网的错误认知
【文章正文】：
Falsehoods Programmers Believe About LANs
程序员对局域网的错误认知
Each entry is phrased as the falsehood. Some of these may sometimes be true and sometimes be false.
每条陈述均为错误假设。其中部分情况可能时而成立，时而不成立。
NAT
网络地址转换（NAT）
- My LAN is behind a NAT.
- 我的局域网位于NAT之后。
- I’m only behind one NAT.
- 我只经过一层NAT。
- My LAN isn’t behind a NAT.
- 我的局域网不经过NAT。
- My IPv6 hosts aren’t behind a NAT.
- 我的IPv6主机不经过NAT。
- If I have a RFC 1918 address, I’m behind a NAT.
- 若使用RFC 1918地址则必定经过NAT。
- If I don’t have a RFC 1918 address, I’m not behind a NAT.
- 若未使用RFC 1918地址则必定不经过NAT。
- NAT only translates addresses.
- NAT仅转换地址。
- NAT only translates addresses and ports.
- NAT仅转换地址和端口。
- NAT changes nothing outside of the header.
- NAT不会修改报文头之外的内容。
- NAT is only found on LANs.
- NAT仅存在于局域网中。
Protocols
网络协议
- Only IPv4 is running on my LAN.
- 我的局域网仅运行IPv4。
- Only IP is running on my LAN.
- 我的局域网仅运行IP协议。
- Okay, only IP, IPX/SPX, Phase IV, AppleTalk, VINES, NetBEUI, or SNA are running on my LAN.
- 好吧，可能还运行IPX/SPX、Phase IV、AppleTalk、VINES、NetBEUI或SNA协议。
- Seriously?
- 认真的吗？
- I can stop certain types of traffic from using my LAN.
- 我能完全阻止特定流量通过局域网。
- I know what’s running on my LAN.
- 我清楚局域网上运行的所有协议。
MAC addresses
MAC地址
- MAC addresses are globally unique. (They’re supposed to be, but they aren’t.)
- MAC地址全球唯一（本应如此，实则不然）。
- MAC addresses are locally unique.
- MAC地址在本地唯一。
- Different MACs are different devices.
- 不同MAC地址对应不同设备。
- Okay, different MACs are different network interfaces.
- 好吧，不同MAC地址对应不同网络接口。
- MAC addresses can’t be changed.
- MAC地址不可更改。
- MAC addresses can be changed.
- MAC地址可以更改。
- MAC addresses are 48 bits.
- MAC地址为48位。
- The first three bytes are vendor–unique.
- 前三个字节是厂商唯一标识。
- The first three bytes are vendor–unique if it’s a MA-L block.
- 对于MA-L地址块，前三个字节才是厂商唯一标识。
- MAC addresses are unicast.
- MAC地址都是单播地址。
- Only one host answers an ARP request for a given IP.
- 特定IP的ARP请求仅由一台主机响应。
- ARP entries are accurate.
- ARP表项绝对准确。
Reachability and performance
可达性与性能
- The LAN is fast.
- 局域网速度很快。
- The LAN is faster than the Internet.
- 局域网比互联网更快。
- Two hosts on the same subnet can reach each other without leaving the LAN.
- 同子网主机通信不会经过局域网外部。
- Same subnet means two hosts can talk.
- 同子网即意味着主机可互通。
- Wi-Fi and Ethernet clients are equivalent peers on the LAN.
- 无线与有线客户端在局域网中完全对等。
- Wi-Fi and Ethernet clients aren’t equivalent peers on the LAN.
- 无线与有线客户端在局域网中不对等。
- Every device on my LAN has the same MTU.
- 局域网内所有设备MTU相同。
- Hostnames are locally unique.
- 主机名在本地唯一。
- mDNS works.
- mDNS协议总是有效。
DHCP
动态主机配置协议
- There is a DHCP server.
- 网络中必存在DHCP服务器。
- There is one DHCP server.
- 网络中仅存在一台DHCP服务器。
- My address won’t change while I’m using it.
- 使用中的IP地址不会变更。
- The DHCP server and the gateway are the same device.
- DHCP服务器与网关是同一设备。
- DHCP will give me a gateway.
- DHCP必定会分配网关地址。
- DHCP will give me a DNS server.
- DHCP必定会分配DNS服务器。
- 169.254.0.0/16 means DHCP failed.
- 169.254.0.0/16地址即表示DHCP失败。
IP addresses
IP地址
- Every host has one IP address.
- 每台主机只有一个IP地址。
- My LAN uses RFC 1918 IP addresses.
- 我的局域网使用RFC 1918私有地址。
- My LAN uses private IP addresses.
- 我的局域网使用私有IP地址。
- My LAN uses IP addresses.
- 我的局域网使用IP地址。