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binsys 楼主提到的 192.0.2.1 属于 RFC5737 保留的文档用途地址。
> Addresses within the TEST-NET-1, TEST-NET-2, and TEST-NET-3 blocks
> SHOULD NOT appear on the public Internet and are used without any
> coordination with IANA or an Internet registry [RFC2050]. Network
> operators SHOULD add these address blocks to the list of non-
> routeable address spaces, and if packet filters are deployed, then
> this address block SHOULD be added to packet filters.
>
> These blocks are not for local use, and the filters may be used in
> both local and public contexts.