PVST+和RSTP混合使用

ssffzz1

关掉的话，你就单纯的靠人工来保证无环吧。

ssffzz1

对一些特殊的MAC是要检查的。是一个特殊的MAC前缀01:

要按照你的理论的话，STP BPDU就实现不了了。

ssffzz1

好像是，第7个bit 为1。我没找到可靠的资料。

ssffzz1

呵呵。没什么。技术这个东西就是很微妙的。

所以说没事别搞网络。害人啊。

gdxnfx

原帖由 ssffzz1 于 2009-8-24 20:47 发表
PVST+的PID字段，0X010B
此字段是SNAP封装的TYPE字段，以太网要求小于0X600,用于区分TYPE和LENGTH,此值小于0x600会导致不支持PVST+的设备识别错误而丢弃报文，因此PVST+的BPDU无法透传，PVST+无法正常工作。
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802.1d bpdu :
An IEEE 802.1d Bpdu has the following format:

protocol id:   0000 IEEE 802.1d
version id:    00
bpdu type:     00 config bpdu, 80 tcn bpdu
bit field:     1 byte
  1 : topology change flag
  2 : unused    0
  3 : unused    0
  4 : unused    0
  5 : unused    0
  6 : unused    0
  7 : unused    0
  8 : topology change ack
root priority    2 bytes
root id:         6 bytes
root path cost:  4 bytes
bridge priority: 2 bytes
bridge id:       6 bytes
port id:         2 bytes
message age:     2 bytes in 1/256 secs
max age:         2 bytes in 1/256 secs
hello time:      2 bytes in 1/256 secs
forward delay:   2 bytes in 1/256 secs



Few changes have been introduced by RSTP to the BPDU format. Only two flags, Topology Change (TC) and TC Acknowledgment (TCA), are defined in 802.1D. However, RSTP now uses all six bits of the flag byte that remain in order to perform:

Encode the role and state of the port that originates the BPDU

Handle the proposal/agreement mechanism

Another important change is that the RSTP BPDU is now of type 2, version 2. The implication is that legacy bridges must drop this new BPDU. This property makes it easy for a 802.1w bridge to detect legacy bridges connected to it.