最近看到论坛有几个人问VSS 等问题，VSS 是现在主流的冗余架构，简化了网络拓扑，增加了冗余性，不需要做主备用一，所以一般现在要么低端设备做堆叠，高端做VSS 。 但是VSS 需要哪些条件可能很多人不是很清楚，我分享一下自己的笔记，希望对大家有帮助，也MARK 一下。
1. 软硬件要求：
Virtual Switching System (VSS)
4500-E switches configured with Supervisor Engines 7-E, 7-LE, or 8E support Quad-Supervisor VSS Mode.
引擎
SUP7L-E
SUP7-E
+E and -E chassis can be mixed.
2.VSL
可以用业务板卡的10G口做为VSL ，一般情况用引擎10G口做VSL
The VSL EtherChannel supports both 10-Gigabit Ethernet ports and 1- Gigabit Ethernet ports.
We recommend that you use at least two of the 10-Gigabit/1-Gigabit Ethernet ports to create the VSL
between the two switches. You cannot combine 10-Gigabit and 1-Gigabit Ethernet ports in a VSL port-channel.
3. license
IP BASE 支持VSS ，需要(Sup 7-E and Sup 8-E only)
Enterprise Services 支持VSS，可以 (Sup 7-E, Sup 7L-E, Sup 8-E, and Sup 8L-E)
