生成树

1: 发送配置BPDU的DoS攻击

让我们发送一些配置BPDU，声称自己是根！！！通过持续发送根路径开销为0、桥ID随机生成（因此根ID相同）以及其余字段使用默认值的配置BPDU，我们试图干扰附近的交换机，导致其STP引擎在解析和重新计算时发生DoS。

源MAC：随机生成。
目的MAC：01:80:c2:00:00:00
桥ID：8000:source_mac
根ID：8000:source_mac
Hello时间：2
转发延迟：15
最大老化时间：20
根路径开销：0

<output from the cisco log>
01:20:26: STP: VLAN0001 heard root 32768-d1bf.6d60.097b on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-9ac6.0f72.7118 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-85a3.3662.43dc on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-3d84.bc1c.918e on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b2e2.1a12.dbb4 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-4ba6.2d45.5844 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-deb0.4f14.7288 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-4879.8036.0e24 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-2776.e340.9222 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-299e.de76.c07d on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-d38b.bc5b.e90d on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-78ee.0205.afdb on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b32b.e969.81b1 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b16b.c428.88a3 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-dd01.1436.9044 on Fa0/8
</output>

2: 发送TCN BPDU的DoS攻击

此攻击持续发送TCN BPDU，迫使根交换机发送配置BPDU确认拓扑变化。此外，根交换机还会向树中成员发送拓扑变更通知，这些成员必须重新计算其STP引擎以学习新的变更。

源MAC：随机生成。
目的MAC：01:80:c2:00:00:00

<output from the cisco log>
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
</output>

3: 非DoS攻击：声称根角色

现在我们的目标是获取树的根角色。如何做到呢？只需监听网络找出哪个是根角色，然后开始发送优先级更低的配置BPDU，从而成为根。

源MAC：与被嗅探到的BPDU相同。
目的MAC：与被嗅探到的BPDU相同。
桥ID：嗅探到的桥ID稍作修改，使其优先级更低。
根ID：8000: 与桥ID相同。
Hello时间：与被嗅探到的BPDU相同。
转发延迟：与被嗅探到的BPDU相同。
最大老化时间：与被嗅探到的BPDU相同。
根路径开销：与被嗅探到的BPDU相同。

<output from the cisco log>
01:58:48: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/8
01:58:48:     supersedes 32769-000e.84d5.2280
01:58:48: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/8, cost 19
</output>

4 非DoS攻击：声称非根角色

我们假装是另一台奇怪的交换机，玩弄STP并吹嘘我们的根ID :)

5 导致永恒根选举的DoS攻击

通过发送优先级自动递减的配置BPDU，我们可以在STP树中引起无限次的根选举。这类似于重新计票以确定胜者的选举（还记得佛罗里达吗？）

<output from the cisco log>
00:20:21: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
00:20:21:     supersedes 32769-000e.84d5.2280
00:20:21: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
00:20:23: STP: VLAN0001 heard root 32769-000e.84d3.2280 on Fa0/9
00:20:23:     supersedes 32769-000e.84d4.2280
00:20:23: STP: VLAN0001 new root is 32769, 000e.84d3.2280 on port Fa0/9, cost 19
00:20:25: STP: VLAN0001 heard root 32769-000e.84d2.2280 on Fa0/9
00:20:25:     supersedes 32769-000e.84d3.2280
00:20:25: STP: VLAN0001 new root is 32769, 000e.84d2.2280 on port Fa0/9, cost 19
00:20:27: STP: VLAN0001 heard root 32769-000e.84d1.2280 on Fa0/9
00:20:27:     supersedes 32769-000e.84d2.2280
00:20:27: STP: VLAN0001 new root is 32769, 000e.84d1.2280 on port Fa0/9, cost 19
00:20:29: STP: VLAN0001 heard root 32769-000e.84d0.2280 on Fa0/9
00:20:29:     supersedes 32769-000e.84d1.2280
00:20:29: STP: VLAN0001 new root is 32769, 000e.84d0.2280 on port Fa0/9, cost 19
00:20:31: STP: VLAN0001 heard root 32769-000e.84cf.2280 on Fa0/9
00:20:31:     supersedes 32769-000e.84d0.2280
00:20:31: STP: VLAN0001 new root is 32769, 000e.84cf.2280 on port Fa0/9, cost 19
00:20:33: STP: VLAN0001 heard root 32769-000e.84ce.2280 on Fa0/9
00:20:33:     supersedes 32769-000e.84cf.2280
00:20:33: STP: VLAN0001 new root is 32769, 000e.84ce.2280 on port Fa0/9, cost 19
00:20:35: STP: VLAN0001 heard root 32769-000e.84cd.2280 on Fa0/9
00:20:35:     supersedes 32769-000e.84ce.2280
00:20:35: STP: VLAN0001 new root is 32769, 000e.84cd.2280 on port Fa0/9, cost 19
00:20:37: STP: VLAN0001 heard root 32769-000e.84cc.2280 on Fa0/9
00:20:37:     supersedes 32769-000e.84cd.2280
00:20:37: STP: VLAN0001 new root is 32769, 000e.84cc.2280 on port Fa0/9, cost 19
00:20:39: STP: VLAN0001 heard root 32769-000e.84cb.2280 on Fa0/9
00:20:39:     supersedes 32769-000e.84cc.2280
00:20:39: STP: VLAN0001 new root is 32769, 000e.84cb.2280 on port Fa0/9, cost 19
</output>

6 导致根消失的DoS攻击

这次我们试图耗尽根选举过程。我们先成为STP树中的根，然后停止发送配置BPDU，直到达到max_age秒（通常为20），从而强制进行新的选举过程。

<output from the cisco log>
02:02:43: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:02:43:     supersedes 32769-000e.84d5.2280
02:02:43: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:03: STP: VLAN0001 we are the spanning tree root
02:03:04: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:03:04:     supersedes 32769-000e.84d5.2280
02:03:04: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:04: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:06: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:08: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:10: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:12: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:14: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:16: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:18: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:20: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:22: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:24: STP: VLAN0001 we are the spanning tree root
02:03:24: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:03:24:     supersedes 32769-000e.84d5.2280
02:03:24: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:24: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:26: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:28: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:30: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:32: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:34: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:36: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:38: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:40: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:42: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:44: STP: VLAN0001 we are the spanning tree root
</output>

减缓措施（仅限Cisco）

• 使用端口安全，并在不需要STP的端口上禁用STP。 有关端口安全的信息，请访问以下URL： http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a0080150bcd.html