环路查看端口是否开放

知STP蔡凤2014-02-24发表H3CS5500交换机STP环路保护开启问题分析H3CS5500交换机STP环路保护开启问题分析一、组网描述:实验室模拟设备组网图-图1图1-实验室模式组网图注:该设备是s5500,版本是version5.
20,Release2215二、问题描述:①创建vlan20,SW1和SW2各自G1/0/24透传vlan20,地址分别配置为2.
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1/24,2.
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2/24,并在vlan20上配置vrrpvrid2,虚拟地址2.
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6,在SW1上配置vrrpvrid2priority120;②创建vlan10,SW3和SW4各自G1/0/14透传vlan10,地址分别配置为2.
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3/24,2.
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4/24,并在vlan10上配置vrrpvrid1,虚拟地址2.
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5,在SW4上配置vrrpvrid1priority120;③SW1和SW4各自G1/0/2,并配置成access口,分别允许vlan20,vlan10通过;④SW2和SW3各自G1/0/12,并配置成access口,分别允许vlan20,vlan10通过;三、结果分析:按照图1组网图,在SW4上ping2.
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2有时通,有时不通,这是因为四台交换机之前生成了环路导致;当我们在SW4上使能stp,如配置显示;[SW4]stpenable%Apr2613:42:32:9272000RT4MSTP/6/MSTP_ENABLE:STPisnowenabledonthedevice.
然后在SW4上ping2.
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2,能ping通,[SW4-GigabitEthernet1/0/14]ping2.
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2PING2.
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2:56databytes,pressCTRL_CtobreakReplyfrom2.
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2:bytes=56Sequence=1ttl=255time=3msReplyfrom2.
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2:bytes=56Sequence=2ttl=255time=3msReplyfrom2.
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2:bytes=56Sequence=3ttl=255time=2msReplyfrom2.
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2:bytes=56Sequence=4ttl=255time=3msReplyfrom2.
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2:bytes=56Sequence=5ttl=255time=3ms---2.
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2pingstatistics---5packet(s)transmitted5packet(s)received0.
00%packetlossround-tripmin/avg/max=2/2/3ms当我们关掉stp,配置如下;[SW4]undstpenable%Apr2613:44:48:3442000RT4MSTP/6/MSTP_DISABLE:STPisnowdisabledonthedevice.
[SW4-GigabitEthernet1/0/14]disth#interfaceGigabitEthernet1/0/14portlink-modebridgeportlink-typetrunkundoporttrunkpermitvlan1porttrunkpermitvlan10stpdisable#return然后在SW4上ping2.
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2,不能ping通,[SW4]ping2.
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2PING2.
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2:56databytes,pressCTRL_CtobreakRequesttimeoutRequesttimeoutRequesttimeoutRequesttimeoutRequesttimeout---2.
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2pingstatistics---5packet(s)transmitted0packet(s)received100.
00%packetloss四、处理过程:断开SW3和SW4之间的G1/0/14互联(用命令undoporttrunkpermitvlan10),在SW4上能Ping通2.
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2,在SW4上用命令displaystpbrief查看,结果如下,可以得知开启的stp协议阻塞了端口g1/0/14,使其变成了阻塞端口,这样才没有形成环路.
[SW4-GigabitEthernet1/0/14]disstpbriefMSTIDPortRoleSTPStateProtection0GigabitEthernet1/0/2DESIFORWARDINGNONE0GigabitEthernet1/0/14BACKDISCARDINGNONE五、总结:遇到此类环路问题,首先检查stp是否开启,如果默认开启,当遇到这样的环路stp协议肯定会阻塞某个端口,这是stp环路阻塞保护机制,我们只需要用命令displaystpbrief查看具体是那个端口被阻塞,如果没有开启stp,我们可以在系统视图下用stpenable开启stp功能,在端口视图下查看是否有此配置,并用命令displaystpbrief在系统视图下查看是否生效.