2个3900交换机（命名为SWITCH A和SWITCH B），做链路聚合（都使用ETHERNET 1/0/1和 1/0/2口），并连接2个3100交换机（命名SWITCH C和SWITCH D，A和B都要连接这2个交换机），组成环路。A和B都开启STP，其中A为主根节点，B为备份根节点。网络正常。
但让A掉电后，B不能切换为主节点,网络不通，只有在B上使用PING命令ping C和D上的计算机后，网络才能正常（这时B仍然显示为备份根节点），请问是什么原因？并请看看我的配置有什么问题，希望大家多多建议。大虾们积极帮助哦！！在这先谢谢了 ！！！！

switch c:
<Quidway>sys
[Quidway]sysname switch_c
[switch_c]vlan 3
[switch_c-vlan3]port ethernet 1/0/3 to eth 1/0/24
[switch_c-vlan3]quit

[switch_c]inter ethernet 1/0/1
[switch_c-Ethernet1/0/1]port link-type trunk
[switch_c-Ethernet1/0/1]port trunk permit vlan all
[switch_c-Ethernet1/0/1]inter ethernet 1/0/2
[switch_c-Ethernet1/0/2]port link-type trunk
[switch_c-Ethernet1/0/2]port trunk permit vlan all



switch d:
<Quidway>sys
[Quidway]sysname switch_d
[switch_d]vlan 4
[switch_d-vlan4]port ethernet 1/0/3 to eth 1/0/24
[switch_d-vlan4]quit

[switch_d]inter ethernet 1/0/1
[switch_d-Ethernet1/0/1]port link-type trunk
[switch_d-Ethernet1/0/1]port trunk permit vlan all
[switch_d-Ethernet1/0/1]inter ethernet 1/0/2
[switch_d-Ethernet1/0/2]port link-type trunk
[switch_d-Ethernet1/0/2]port trunk permit vlan all



switch a:
<Quidway>sys
[Quidway]sysname switch_a
[switch_a]stp enable
[switch_a]stp root primary
[switch_a]link-aggregation group 1 mode manual
[switch_a]interface eth 1/0/1
[switch_a-Ethernet1/0/1]port link-a group 1
[switch_a-Ethernet1/0/1]interface eth 1/0/2
[switch_a-Ethernet1/0/2]port link-a group 1

[switch_a-Ethernet1/0/2]rip
[switch_a-rip]network 10.0.0.0

[switch_a-rip]vlan 2
[switch_a-vlan2]port eth 1/0/24
[switch_a-vlan2]vlan 3
[switch_a-vlan3]vlan 4
[switch_a-vlan4]quit

[switch_a]interface vlan-interface 2
[switch_a-Vlan-interface2]ip address 10.0.0.1 24
[switch_a-Vlan-interface2]quit
[switch_a]interface vlan-interface 3
[switch_a-Vlan-interface3]ip address 10.0.1.1 24
[switch_a-Vlan-interface3]quit
[switch_a]interface vlan-interface 4
[switch_a-Vlan-interface4]ip address 10.0.2.1 24
[switch_a-Vlan-interface4]quit

[switch_a]interface eth 1/0/3
[switch_a-Ethernet1/0/3]port link-type trunk
[switch_a-Ethernet1/0/3]port trunk permit vlan all

[switch_a-Ethernet1/0/3]interface eth 1/0/4
[switch_a-Ethernet1/0/4]port link-type trunk
[switch_a-Ethernet1/0/4]port trunk permit vlan all



switch b:
<Quidway>sys
[Quidway]sysname switch_b
[switch_b]stp enable
[switch_b]stp root secondary
[switch_b]link-a group 1 mode manual
[switch_b]interface eth 1/0/1
[switch_b-Ethernet1/0/1]port link-a group 1
[switch_b-Ethernet1/0/1]interface eth 1/0/2
[switch_b-Ethernet1/0/2]port link-a group 1

[switch_b-Ethernet1/0/2]rip
[switch_b-rip]network 10.0.0.0

[switch_b-rip]vlan 2
[switch_b-vlan2]vlan 3
[switch_b-vlan3]vlan 4
[switch_b-vlan4]quit

[switch_b]interface vlan-interface 2
[switch_b-Vlan-interface2]ip address 10.0.0.1 24
[switch_b-Vlan-interface2]interface vlan-interface 3
[switch_b-Vlan-interface3]ip address 10.0.1.1 24
[switch_b-Vlan-interface3]interface vlan-interface 4
[switch_b-Vlan-interface4]ip address 10.0.2.1 24
[switch_b-Vlan-interface4]quit

[switch_b]interface eth 1/0/3
[switch_b-Ethernet1/0/3]port link-type trunk
[switch_b-Ethernet1/0/3]port trunk permit vlan all
[switch_b-Ethernet1/0/3]interface eth 1/0/4
[switch_b-Ethernet1/0/4]port link-type trunk
[switch_b-Ethernet1/0/4]port trunk permit vlan all



route a:
<Quidway>sys
[Quidway]sysname router_a
[router_a]interface ethernet 0/0
[router_a-Ethernet0/0]ip address 10.0.0.2 24
[router_a-Ethernet0/0]quit

[router_a]rip
[router_a-rip]network 10.0.0.0

另：A DOWN掉后，B需要8－9分钟才能让网络联通（B仍然显示为备份根节点），同样，A   down后再UP 也需要8－9分钟后A才能正常工作，这个时间是不是太长了点？？？（都是今天刚刚验证的哈）什么原因呢？谢谢大家！！！

同时问大虾门，如图的这种网络结构现实中使用吗？多吗？谢谢，如果没，现实使用的主要是那种，能给个图和配置就感激涕零了！！！！！！！