The first command allows port 22 (TCP is the default option) from a source of your IP address.

第一条命令认可来自您的IP地址的一个源的端口22 (TCP是默认选项)。

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During login, a host may perform a reverse lookup on the IP address of the source address on the packets it receives.

在登录期间，主机可能会对它收到的数据包的源地址的IP地址执行反向查找。

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The problem that can occur with TCP is when a rogue client forges an IP packet with a bogus source address, then floods a server with TCP SYN packets.

当恶意客户机使用虚假的源地址来伪造一个 IP 报文时，TCP 就会出现问题了，这会大量 TCP SYN 报文攻击服务器。

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