私网STP在公网的透传

STP（Spanning Tree Protocol）是生成树协议的缩写。它是一种二层管理协议，通过有选择性地阻塞网络冗余链路来达到消除网络二层环路的目的。然而，按照802．1D标准BPDU不带VLANTAG，而且要求所有网桥不能转发BPDU；带Tag的BPDU报文协议报文都是非法报文，不能保证它能在公网上被正确透传。当用户想让一个BPDU报文透明穿越一个承载网络时，这样分居于两地的同一企业的分支就可以通过隧道的透传获得彼此STP协议的信息，从而有效地避免了环路的产生。通过对该协议的研究，在二层交换网络中提供一种简单的方式来实现私网的STPBPDU报文在公网的透传；即在二层交换网络的入接口使能BPDUTunnel，利用QinQ技术来实现私网BPUD报文在公网的透传。

Transparent Transmission of Private Spanning Tree Protocol through Public Network

STP(Spanning Tree Protocol)is a protocol of layer 2.It is used to eliminate the ring cycle of layer-2 by choosing the redundancy physical.However,according to the standard of 802.1D,it is impossible to forward BPDU segment with VLAN TAG.The BPDU segment with Tag is unlawful,so it can not made sure the segment come across the public network transmission transparently.When the user want to come across the carried network,it will made the company which separate in the different place got the message quickly,it also avoid of the ring of cycle.This passage is mainly pay attention to the research of this protocol which gives a simple and quick way to realize the transparent transmission of BPDU segment in the private network.The way is using of QinQ technical which provide a transparent Tunnel to make this transmission come true.