技术上说，VPN是指将物理上分布在不同地点的网络，通过公用骨干网连接而形成的逻辑上的虚拟子网。

In technology, VPN means the networks locating in the different places are connected by main public networks, which shape the logic networks.

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如果可以使用虚拟LAN (VLAN)中继，就可以通过同一个物理适配器同时访问多个子网，但是这种方法无法享有这一好处。

If virtual LAN (VLAN) trunking is available, where multiple network subnets can be accessed simultaneously through the same physical adapter, this method does not use that benefit.

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在 Linux 和 Solaris 系统上，可以在一块物理以太网卡上创建多个虚拟接口，让它们连接到不同子网上的 IP 地址。

On both Linux and Solaris, you can create multiple virtual interfaces to IP addresses on different subnets on one physical ethernet card.

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