MAC地址表故障处理手册目录1-11 MAC地址表故障处理··························································································································1-11.1 源MAC地址攻击导致端口流量瞬断故障处理························································································ 1-11.1.1 故障描述 ······························································································································1.1.2 故障处理步骤··························································································································1-1······ 1-31.2 故障诊断命令·······························································································································1 MAC地址表故障处理1.1 源MAC地址攻击导致端口流量瞬断故障处理1.1.1 故障描述如图1-1所示，Switch下接DSLAM（Digital Subscriber Line Access Multiplexer，数字用户线接入复用器），Switch上接BAS（Broadband Access Server，宽带接入服务器），由BAS终结用户的拨号PPPoE报文。
在Switch上配置灵活QinQ功能，对应的用户侧VLAN为824，网络侧VLAN为1003。
BAS上作为网关的MAC地址为0090-1aa0-d47a。
故障现象为：DSLAM下挂用户不定时大规模掉线。
出现问题时，发现端口Ethernet3/0/4的流量急剧下降。
大约5分钟左右，端口Ethernet3/0/4的流量开始慢慢回升，证明此时大规模掉线已经结束，DSLAM下挂用户又在逐步恢复连接，网络在逐步恢复正常状态。
图1-1源MAC地址攻击导致端口流量瞬断故障处理组网图1.1.2 故障处理步骤(1) 检查接口信息执行display interface命令显示端口Ethernet3/0/4的相关信息：<Switch> display interface ethernet 3/0/4Ethernet3/0/4 current state: UPIP Packet Frame Type: PKTFMT_ETHNT_2, Hardware Address: 000f-e200-8048Description: Ethernet3/0/4 InterfaceLoopback is not setMedia type is twisted pair, port hardware type is 100_BASE_TX100Mbps-speed mode, full-duplex modeLink speed type is autonegotiation, link duplex type is autonegotiationFlow-control is not enabledThe Maximum Frame Length is 9022Broadcast MAX-ratio: 100%Unicast MAX-ratio: 100%Multicast MAX-ratio: 100%Allow jumbo frame to passPVID: 100Mdi type: autoPort link-type: trunkVLAN passing : 824VLAN permitted: 824Trunk port encapsulation: IEEE 802.1qPort priority: 0Last clearing of counters: NeverPeak value of input: 4 bytes/sec, at 2012-04-26 12:07:48Peak value of output: 81 bytes/sec, at 2012-04-26 12:09:24Last 300 seconds input: 1 packets/sec 147 bytes/secLast 300 seconds output: 1 packets/sec 179 bytes/secInput (total): 271 packets, 12250 bytes0 unicasts, 150 broadcasts, 121 multicasts, 0 pausesInput (normal): 271 packets, 12250 bytes0 unicasts, 150 broadcasts, 121 multicasts, 0 pausesInput: 0 input errors, 0 runts, 0 giants, 0 throttles0 CRC, 0 frame, - overruns, 0 aborts- ignored, - parity errorsOutput (total): 1522 packets, 183608303 bytes0 unicasts, 13 broadcasts, 860 multicasts, 0 pausesOutput (normal): 1522 packets, - bytes0 unicasts, 13 broadcasts, 860 multicasts, 0 pausesOutput: 0 output errors, - underruns, 1 buffer failures0 aborts, 0 deferred, 0 collisions, 0 late collisions0 lost carrier, - no carrier可以看到，端口在故障时只有组播和广播报文的记数。