網(wǎng)絡(luò)故障排除場景案例附件列表文件1參

場景案例1：參考答案本場景案例共設(shè)置了七個故障點，假設(shè)如下：公司換了兩家新的ISP服務(wù)商，周末進行了線路切換。不排除網(wǎng)絡(luò)管理員對網(wǎng)絡(luò)做了其他操作。周一的上午，你在辦公座位接到電話，一名公司的員工說他無法通過終端（PC7）訪問互聯(lián)網(wǎng)（Server1）。學(xué)員通過本案例的練習(xí)，可以學(xué)會如何靈活運用所學(xué)到的網(wǎng)絡(luò)故障排除方法。故障背景故障排除案例1

-故障背景公司換了兩家新的ISP服務(wù)商，周末進行了線路切換。不排除網(wǎng)絡(luò)管理員對網(wǎng)絡(luò)做了其他操作。周一上午你接到用戶的故障報告。故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障報告故障周一的上午，你在辦公座位接到電話，一名公司的員工說他無法通過終端（PC7）訪問互聯(lián)網(wǎng)（Server1），希望得到你的技術(shù)支持。Internet報告故障-詢問內(nèi)容故障報告者姓名、所在的部門、職位級別、工作負責(zé)所的內(nèi)容、使用電腦的位置（樓層、房間、無線接入還是有線接入）、在使用電腦訪問什么網(wǎng)站時發(fā)現(xiàn)的問題。故障時間故障是突發(fā)的、偶爾的、還是頻繁的。用戶操作出現(xiàn)故障之前和之后，用戶對自己的終端做了哪些操作，如是否更改了IP地址和DNS、是否安裝了桌面防火墻軟件、安全控制軟件等。報告故障-記錄內(nèi)容故障報告者某設(shè)計部普通員工，需要經(jīng)常使用桌面PC收集互聯(lián)網(wǎng)上的設(shè)計素材。使用PC7。故障時間故障是周一上班后發(fā)現(xiàn)的。周五下班前還能正常訪問互聯(lián)網(wǎng)。用戶操作上周三曾經(jīng)安裝了某設(shè)計軟件，之后還能訪問網(wǎng)絡(luò)。每次都是上班后直接打開電腦使用的，不需要進行額外的設(shè)置。確認故障你作為網(wǎng)絡(luò)管理員登錄用戶的PC，發(fā)現(xiàn)確實無法訪問互聯(lián)網(wǎng)。你對服務(wù)器的IP地址發(fā)起了PING操作，發(fā)現(xiàn)無法PING通。于是你的判斷是“存在連通性故障”。你決定試一下新學(xué)習(xí)到的“結(jié)構(gòu)化的網(wǎng)絡(luò)故障排除流程”和“以業(yè)務(wù)流量路徑為核心的故障排除思想”在實際工作中的應(yīng)用效果，準(zhǔn)備按照步驟逐步進行故障排除。確認故障-記錄內(nèi)容確認方法登錄PC7，嘗試打開網(wǎng)頁失敗。對某互聯(lián)網(wǎng)服務(wù)器的IP地址發(fā)起了PING操作，發(fā)現(xiàn)無法PING通。確認結(jié)果PC7無法訪問互聯(lián)網(wǎng)，存在連通性故障。收集信息首先確定業(yè)務(wù)流量路徑。得到二層和三層的流量正常走向。用“分塊法”和“分段法”了解每個節(jié)點上應(yīng)用到的二層技術(shù)、三層技術(shù)。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6LSW4確定業(yè)務(wù)流量路徑DHCPServer用“分塊法”和“分段法”了解每個節(jié)點上應(yīng)用到的二層技術(shù)、三層技術(shù)。收集信息-各節(jié)點所應(yīng)用的網(wǎng)絡(luò)技術(shù)PC7IP、DHCPLSW4IP、OSPF、DHCPRealy、MSTP、VLAN、TrunkCSW2IP、VRRP、Trunk、鏈路聚合、OSPFAR1IP、OSPF、靜態(tài)路由、路由重分布。Server1IP（支持ping）、http判斷分析用分段法判斷，網(wǎng)絡(luò)故障可能出現(xiàn)在從操作者到PC、交換機、路由器、服務(wù)器中的某一個節(jié)點。結(jié)合分塊法判斷，每個節(jié)點上可能有導(dǎo)致連通性故障的軟件或硬件原因。這時理論上可用替換法替換中間任何一臺設(shè)備，但事實上受條件限制，多數(shù)情況下只能替換終端嘗試連接。原因列表可能是操作者的操作失誤或PC本身的故障。可能是交換機、路由器到服務(wù)器之間的鏈路故障?？赡芙粨Q機、路由器、服務(wù)器的硬件故障。使用方法：分段法登錄PC7，執(zhí)行和用戶相同的操作。得到的結(jié)果是一樣的，所以可以排除操作者失誤的可能性。原因列表

-操作者失誤PC7:[PC>pingPing:32databytes,PressCtrl_CtobreakFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:Destinationhostunreachable---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>使用方法：自底向上法、替換法、分段法。替換其他終端嘗試訪問相同的網(wǎng)站，可以發(fā)現(xiàn)同樣不能連通。為了確定故障發(fā)生的范圍，分別從同部門（Vlan40）的PC8、不同部門（Vlan30）的PC5上發(fā)起訪問，故障是普遍存在的。所以應(yīng)該可以排除PC本身的硬件原因。原因列表-PC硬件故障PC5:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>PC7:[PC>pingPing:32databytes,PressCtrl_CtobreakFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:Destinationhostunreachable---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>原因列表-再次判斷分析由于所有PC都是通過DHCP方式獲取IP地址，所以此時懷疑是DHCP服務(wù)器故障。由于周末進行了ISP鏈路切換，懷疑企業(yè)廣域網(wǎng)出口鏈路故障。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClient??排查廣域網(wǎng)出口鏈路?使用方法：自底向上法。查看PC7的IP地址設(shè)置。發(fā)現(xiàn)并不是DHCP獲取方式，而是被人手工配制了錯誤的IP地址。原因列表-IP地址獲取故障經(jīng)排障評估，排除此故障無風(fēng)險。將客戶端獲取IP地址的方式改為DHCP。IP地址獲取故障-修改客戶端配置故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障經(jīng)測試，仍然無法訪問外部網(wǎng)站。發(fā)現(xiàn)通過DHCP方式獲取到的IP地址有問題。IP地址獲取故障-解決故障？PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>PC7:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fedd:5659IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:52Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-DD-56-59DNSserver........................:PC>InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClientIP地址

獲取故障根據(jù)DHCPRelay方式獲取IP地址的原理，正常情況下數(shù)據(jù)報文的轉(zhuǎn)發(fā)方式如圖所示。錯誤的IP地址-DHCP業(yè)務(wù)流量路徑InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClient?DHCP

業(yè)務(wù)流量路徑由于是通過DHCPRelay方式獲取到的IP地址，問題可能是存在于DHCPServer或者DHCPRelay、以及數(shù)據(jù)流所經(jīng)過的網(wǎng)絡(luò)設(shè)備。為了明確定位故障的根源，首先需要確定故障的范圍。從接入層開始，逐步排查。錯誤的IP地址-原因列表InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClient??????????接入層排查?使用方法：對比配置法、替換法。通過對比其他PC的IP地址，發(fā)現(xiàn)只有Vlan40的用戶存在IP地址獲取錯誤的問題。錯誤的IP地址-判斷分析(1)PC7:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fedd:5659IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:52Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-DD-56-59DNSserver........................:PC>錯誤的IP地址-判斷分析(2)PC1:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fe2d:32fcIPv6address......................:::/128IPv6gateway......................:::IPv4address......................:54Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-2D-32-FCDNSserver........................:PC>PC3:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fe79:61c8IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:53Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-79-61-C8DNSserver........................:PC>PC5:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fe50:3e74IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:53Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-50-3E-74DNSserver........................:PC>通過對比配置法，可以確定故障局限于VLAN40。根據(jù)DHCP協(xié)議原理（客戶端發(fā)送廣播報文），可以知道VLAN30的DHCPRelay取代了VLAN40的DHCPRelay響應(yīng)了DHCP的發(fā)現(xiàn)報文。而這個報文是二層廣播的，所以判斷現(xiàn)在PC7和VLAN30的DHCPRelay在同一個VLAN內(nèi)。檢查LSW4上對應(yīng)端口的配置。錯誤的IP地址-判斷分析(3)[LSW4-Ethernet0/0/3]displaythis#interfaceEthernet0/0/3portlink-typeaccessportdefaultvlan30#錯誤的IP地址-修正VLAN端口配置將LSW4上與PC7相連的端口劃入正確的VLAN。[LSW4-Ethernet0/0/3]displaythis#interfaceEthernet0/0/3portlink-typeaccessportdefaultvlan30#[LSW4-Ethernet0/0/3]displaythis#interfaceEthernet0/0/3portlink-typeaccessportdefaultvlan40#故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障錯誤的IP地址-解決故障？關(guān)機然后再重新啟動PC7，查看PC7是否獲取到了正確的IP地址，答案是否定的。PC7:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fedd:5659IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-DD-56-59DNSserver........................:PC>無法獲取IP地址-DHCP業(yè)務(wù)流量路徑對此故障現(xiàn)象首先了解正常情況下流量的路徑。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClient?DHCPRelay

業(yè)務(wù)流量路徑無法獲取IP地址-原因列表由于是通過DHCPRelay方式獲取到的IP地址，問題可能是存在于DHCPServer或者DHCPRelay、以及數(shù)據(jù)流所經(jīng)過的網(wǎng)絡(luò)設(shè)備。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6VLAN10/24VLAN20/24VLAN30/24VLAN40/241001.4/301002.8/301003.12/301004.16/301007.24/301008.28/301009.32/30VLAN100X192.168.2.X/30VLAN200X192.168.3.X/302001.4/301006.20/30TrunkTrunkTrunkTrunkDHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClient???????可能的故障點?無法獲取IP地址-逐一排查使用方法：分段法。根據(jù)DHCPRelay協(xié)議的原理，將排障范圍分成三段：DHCPRelay、途經(jīng)設(shè)備（含路由問題）、DHCPServer。使用方法：分塊法。對分段法劃分的每個設(shè)備使用分塊法查看協(xié)議配置、接口狀態(tài)等信息。使用方法：對比配置法。由于其他VLAN用戶獲取到的IP地址是正確的，所以可以對比其他設(shè)備與本設(shè)備（LSW4）的配置差異。分段法InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6DHCPRelayDHCPRelayDHCPRelayDHCPRelayDHCPServerDHCPClientLSW3配置：無法獲取IP地址-對比配置法LSW4配置：[LSW3]displaycurrent-configuration<--

此處省略其他輸出信息

-->#dhcpenable#dhcpservergroupdhcpgroup30dhcp-server0#interfaceVlanif30ipaddressdhcpselectrelaydhcprelayserver-selectdhcpgroup30#[LSW4]displaycurrent-configuration<--

此處省略其他輸出信息-->#dhcpenable#dhcpservergroupdhcpgroup40dhcp-server0#interfaceVlanif40ipaddressdhcpselectrelay#無法獲取IP地址-修正DHCPRelay配置通過對比配置法，發(fā)現(xiàn)LSW4上VLAN40的DHCP中繼接口并沒有綁定DHCP服務(wù)器組。修改為正確的配置。#interfaceVlanif40ipaddressdhcpselectrelay#[LSW4-Vlanif40]displaythis#interfaceVlanif40ipaddressdhcpselectrelaydhcprelayserver-selectdhcpgroup40#return無法獲取IP地址-解決故障經(jīng)過檢查，發(fā)現(xiàn)PC7已經(jīng)通過DHCP獲取到了正確的IP地址、網(wǎng)關(guān)、DNS。PC7:PC>ipconfigLinklocalIPv6address...........:fe80::5689:98ff:fedd:5659IPv6address......................:::/128IPv6gateway......................:::IPv4address......................:53Subnetmask.......................:Gateway...........................:Physicaladdress..................:54-89-98-DD-56-59DNSserver........................:PC>故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障新的問題解決了通過DHCP獲取IP地址的問題后，現(xiàn)在嘗試從PC7上連接遠端的WEB網(wǎng)站，發(fā)現(xiàn)仍然無法連通。PC7:[PC>pingPing:32databytes,PressCtrl_CtobreakFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:DestinationhostunreachableFrom:Destinationhostunreachable---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-回顧業(yè)務(wù)流量路徑PC7訪問WEB網(wǎng)站的報文路徑如圖所示。根據(jù)本案例前面分析可能原因，使用分段法按接入層、匯聚層、核心層依次進行排除。網(wǎng)絡(luò)連通性故障-接入層排查由于PC7已經(jīng)獲取到了IP地址，可以通過網(wǎng)絡(luò)層ping的方式來測試接入層是否正常。ping同VLAN的其他IP地址，測試本VLAN內(nèi)的連通性。ping網(wǎng)關(guān)的IP地址，測試離開本VLAN的網(wǎng)關(guān)的連通性。網(wǎng)絡(luò)連通性故障-接入層排查從PC7pingLSW4、CSW1、CSW2上的VLAN40接口IP地址，發(fā)現(xiàn)連通性正常。CSW1:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=63msFrom:bytes=32seq=2ttl=255time=47msFrom:bytes=32seq=3ttl=255time=47msFrom:bytes=32seq=4ttl=255time=47msFrom:bytes=32seq=5ttl=255time=63ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=47/53/63msPC>CSW2:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=31msFrom:bytes=32seq=2ttl=255time=62msFrom:bytes=32seq=3ttl=255time=47msFrom:bytes=32seq=4ttl=255time=62msFrom:bytes=32seq=5ttl=255time=32ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=31/46/62msPC>LSW4:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=32msFrom:bytes=32seq=2ttl=255time=16msFrom:bytes=32seq=3ttl=255time=16msFrom:bytes=32seq=4ttl=255time=16msFrom:bytes=32seq=5ttl=255time<1ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=0/16/32msPC>網(wǎng)絡(luò)連通性故障-匯聚層排查(1)由于PC7的網(wǎng)關(guān)是匯聚層的VRRP虛擬IP地址，所以開始排查是否是匯聚層的問題。從PC7ping網(wǎng)關(guān)的IP地址，發(fā)現(xiàn)不通。PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:Destinationhostunreachable---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-匯聚層排查(2)使用對比法觀察其他VLAN的PC能夠ping通自己網(wǎng)關(guān)，所以判斷是VLAN40內(nèi)的VRRP虛擬IP網(wǎng)關(guān)地址可能存在問題。根據(jù)VRRP的協(xié)議原理，排查CSW1和CSW2的問題。PC3:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=16msFrom:bytes=32seq=2ttl=255time=47msFrom:bytes=32seq=3ttl=255time=32msFrom:bytes=32seq=4ttl=255time=31msFrom:bytes=32seq=5ttl=255time=47ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=16/34/47msPC>PC5:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=78msFrom:bytes=32seq=2ttl=255time=32msFrom:bytes=32seq=3ttl=255time=47msFrom:bytes=32seq=4ttl=255time=31msFrom:bytes=32seq=5ttl=255time=31ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=31/43/78msPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:DestinationhostunreachableFrom53:Destinationhostunreachable---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-匯聚層VRRP報文路徑根據(jù)網(wǎng)絡(luò)的規(guī)劃設(shè)計，匯聚層交換機CSW1和CSW2之間會交換VRRP協(xié)議報文。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3LSW4CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6Vlan1020MasterVlan3040BackupVlan3040MasterVlan1020BackupVirtualIPAddress:VirtualIPAddress:VirtualIPAddress:VirtualIPAddress:匯聚層

VRRP報文路徑DHCPServer網(wǎng)絡(luò)連通性故障-匯聚層排查(3)使用displayvrrpbrief命令，發(fā)現(xiàn)CSW1和CSW2上VLAN40的VRRP虛擬IP是錯誤的。[CSW1]displayvrrpbriefVRIDStateInterfaceTypeVirtualIP----------------------------------------------------------------1MasterVlanif10Normal1MasterVlanif20Normal1BackupVlanif30Normal1BackupVlanif40Normal0----------------------------------------------------------------Total:4Master:2Backup:2Non-active:0[CSW2]displayvrrpbriefVRIDStateInterfaceTypeVirtualIP----------------------------------------------------------------1BackupVlanif10Normal1BackupVlanif20Normal1MasterVlanif30Normal1MasterVlanif40Normal0----------------------------------------------------------------Total:4Master:2Backup:2Non-active:0[CSW1-Vlanif40]displaythis#interfaceVlanif40ipaddressvrrpvrid1virtual-ip0#return[CSW2-Vlanif40]displaythis#interfaceVlanif40ipaddressvrrpvrid1virtual-ip0vrrpvrid1priority120#return[CSW1-Vlanif40]displaythis#interfaceVlanif40ipaddressvrrpvrid1virtual-ip#return[CSW2-Vlanif40]displaythis#interfaceVlanif40ipaddressvrrpvrid1virtual-ipvrrpvrid1priority120#return網(wǎng)絡(luò)連通性故障-匯聚層排查(4)檢查兩臺設(shè)備上的VRRP配置命令發(fā)現(xiàn)存在配置錯誤。修正錯誤的配置。網(wǎng)絡(luò)連通性故障-匯聚層排查(5)再次執(zhí)行displayvrrpbrief命令，發(fā)現(xiàn)輸出結(jié)果正常。[CSW1]displayvrrpbriefVRIDStateInterfaceTypeVirtualIP----------------------------------------------------------------1MasterVlanif10Normal1MasterVlanif20Normal1BackupVlanif30Normal1BackupVlanif40Normal----------------------------------------------------------------Total:4Master:2Backup:2Non-active:0[CSW2]displayvrrpbriefVRIDStateInterfaceTypeVirtualIP----------------------------------------------------------------1BackupVlanif10Normal1BackupVlanif20Normal1MasterVlanif30Normal1MasterVlanif40Normal----------------------------------------------------------------Total:4Master:2Backup:2Non-active:0網(wǎng)絡(luò)連通性故障-匯聚層排查(6)在PC7上執(zhí)行測試，發(fā)現(xiàn)可以ping通網(wǎng)關(guān)。說明VRRP的故障已經(jīng)排除。PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=255time=62msFrom:bytes=32seq=2ttl=255time=31msFrom:bytes=32seq=3ttl=255time=47msFrom:bytes=32seq=4ttl=255time=31msFrom:bytes=32seq=5ttl=255time=31ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=31/40/62msPC>故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障網(wǎng)絡(luò)連通性故障-問題解決？在PC7上嘗試訪問WEB服務(wù)器，發(fā)現(xiàn)仍然存在連通性問題。PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-核心層排查(1)繼續(xù)使用分段法自遠至近進行故障排除。嘗試ping兩個ISP的網(wǎng)關(guān)地址，發(fā)現(xiàn)都無法訪問。InternetISP1ISP2ISP1ISP2網(wǎng)絡(luò)連通性故障-核心層排查(2)嘗試ping本地出口路由器的IP地址，發(fā)現(xiàn)都無法訪問。AR1AR2PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-核心層排查(3)嘗試ping網(wǎng)關(guān)路由器內(nèi)網(wǎng)方向的IP地址，發(fā)現(xiàn)可以正常訪問。AR1AR2PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=254time=47msFrom:bytes=32seq=2ttl=254time=62msFrom:bytes=32seq=3ttl=254time=46msFrom:bytes=32seq=4ttl=254time=78msFrom:bytes=32seq=5ttl=254time=93ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=46/65/93msPC>PC7:PC>ping8Ping8:32databytes,PressCtrl_CtobreakFrom8:bytes=32seq=1ttl=254time=78msFrom8:bytes=32seq=2ttl=254time=63msFrom8:bytes=32seq=3ttl=254time=63msFrom8:bytes=32seq=4ttl=254time=47msFrom8:bytes=32seq=5ttl=254time=47ms---8pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=47/59/78msPC>網(wǎng)絡(luò)連通性故障-核心層排查(4)故障點現(xiàn)在已經(jīng)定位到兩臺出口路由器。使用自底向上法，登錄路由器查看接口狀態(tài)。發(fā)現(xiàn)連接ISP的接口被關(guān)閉了。[AR1]displayinterfaceGigabitEthernet2/0/0GigabitEthernet2/0/0currentstate:AdministrativelyDOWNLineprotocolcurrentstate:DOWNDescription:HUAWEI,ARSeries,GigabitEthernet2/0/0InterfaceRoutePort,TheMaximumTransmitUnitis1500InternetAddressis/24<--此處省略其他輸出信息-->[AR2]displayinterfaceGigabitEthernet2/0/0GigabitEthernet2/0/0currentstate:AdministrativelyDOWNLineprotocolcurrentstate:DOWNDescription:HUAWEI,ARSeries,GigabitEthernet2/0/0InterfaceRoutePort,TheMaximumTransmitUnitis1500InternetAddressis/24<--此處省略其他輸出信息-->網(wǎng)絡(luò)連通性故障-核心層排查(5)在兩臺路由器的相應(yīng)接口上執(zhí)行undoshutdown命令，修正接口配置。AR1AR2[AR1]interfaceGigabitEthernet2/0/0[AR1-GigabitEthernet2/0/0]undoshutdown[AR2]interfaceGigabitEthernet2/0/0[AR2-GigabitEthernet2/0/0]undoshutdown網(wǎng)絡(luò)連通性故障-路由器接口故障在PC7上測試到兩臺路由器出接口的連通性，發(fā)現(xiàn)正常了。AR1AR2PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=254time=78msFrom:bytes=32seq=2ttl=254time=93msFrom:bytes=32seq=3ttl=254time=109msFrom:bytes=32seq=4ttl=254time=62msFrom:bytes=32seq=5ttl=254time=62ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=62/80/109msPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=254time=78msFrom:bytes=32seq=2ttl=254time=78msFrom:bytes=32seq=3ttl=254time=63msFrom:bytes=32seq=4ttl=254time=62msFrom:bytes=32seq=5ttl=254time=47ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=47/65/78msPC>故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障網(wǎng)絡(luò)連通性故障-問題解決？在PC7上嘗試訪問WEB服務(wù)器，發(fā)現(xiàn)仍然存在連通性問題。PC7:PC>pingPing:32databytes,PressCtrl_CtobreakRequesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!Requesttimeout!---pingstatistics---5packet(s)transmitted0packet(s)received100.00%packetlossPC>網(wǎng)絡(luò)連通性故障-路由排查(1)嘗試ping兩個ISP的網(wǎng)關(guān)地址，發(fā)現(xiàn)可以訪問。PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=253time=94msFrom:bytes=32seq=2ttl=253time=141msFrom:bytes=32seq=3ttl=253time=94msFrom:bytes=32seq=4ttl=253time=109msFrom:bytes=32seq=5ttl=253time=78ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=78/103/141msPC>PC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=253time=63msFrom:bytes=32seq=2ttl=253time=62msFrom:bytes=32seq=3ttl=253time=47msFrom:bytes=32seq=4ttl=253time=62msFrom:bytes=32seq=5ttl=253time=78ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=47/62/78msPC>InternetISP1ISP2ISP1ISP2網(wǎng)絡(luò)連通性故障-路由排查(2)訪問與內(nèi)網(wǎng)相關(guān)的網(wǎng)段是正常的，說明內(nèi)網(wǎng)的路由是正常的。訪問外部的網(wǎng)站是不正常的，說明到外網(wǎng)的路由是不正常的。內(nèi)網(wǎng)每個三層設(shè)備都需要知道到外網(wǎng)的路由，到底是哪里出了問題？按照“從近到遠”的方向，用分段法進行排除。InternetISP1ISP2PC1PC2PC3PC4PC5LSW1PC6PC7PC8LSW2LSW3CSW1CSW2AR1AR2ISP1ISP2Server1Server2Server3LSW5LSW6LSW4路由排查DHCPServer網(wǎng)絡(luò)連通性故障-路由排查(3)查看LSW4的路由表，發(fā)現(xiàn)存在通過OSPF學(xué)習(xí)到的默認路由，下一跳路由器分別是CSW1和CSW2。[LSW4]displayiprouting-tableRouteFlags:R-relay,D-downloadtofib------------------------------------------------------------------------------RoutingTables:PublicDestinations:30Routes:46Destination/MaskProtoPreCostFlagsNextHopInterface/0O_ASE1501DVlanif40O_ASE1501DVlanif40<--此處省略其他輸出信息-->網(wǎng)絡(luò)連通性故障-路由排查(4)查看CSW1和CSW2的路由表，發(fā)現(xiàn)存在通過OSPF學(xué)習(xí)到的默認路由，下一跳路由器分別是AR1和AR2。[CSW1]displayiprouting-tableRouteFlags:R-relay,D-downloadtofib------------------------------------------------------------------------------RoutingTables:PublicDestinations:35Routes:43Destination/MaskProtoPreCostFlagsNextHopInterface/0O_ASE1501D0Vlanif1002O_ASE1501DVlanif1001<--此處省略其他輸出信息-->[CSW2]displayiprouting-tableRouteFlags:R-relay,D-downloadtofib------------------------------------------------------------------------------RoutingTables:PublicDestinations:35Routes:43Destination/MaskProtoPreCostFlagsNextHopInterface/0O_ASE1501D8Vlanif1004O_ASE1501D4Vlanif1003<--此處省略其他輸出信息-->網(wǎng)絡(luò)連通性故障-路由排查(5)查看AR1和AR2的相關(guān)配置，發(fā)現(xiàn)兩臺設(shè)備的靜態(tài)路由指向的是以前的ISP。[AR1]displaycurrent-configuration<--

此處省略其他輸出信息

-->#ospf1default-route-advertisealwaysareanetworknetworknetworknetwork2network4network2#iproute-static#[AR2]displaycurrent-configuration<--

此處省略其他輸出信息

-->#ospf1default-route-advertisealwaysareanetworknetworknetworknetwork6network0network8#iproute-static#網(wǎng)絡(luò)連通性故障-路由排查(6)修正AR1和AR2的靜態(tài)路由。PC7可以正常訪問互聯(lián)網(wǎng)了。[AR1]undoiproute-static[AR1]iproute-static[AR2]undoiproute-static[AR2]iproute-staticPC7:PC>pingPing:32databytes,PressCtrl_CtobreakFrom:bytes=32seq=1ttl=124time=94msFrom:bytes=32seq=2ttl=124time=47msFrom:bytes=32seq=3ttl=124time=47msFrom:bytes=32seq=4ttl=124time=78msFrom:bytes=32seq=5ttl=124time=78ms---pingstatistics---5packet(s)transmitted5packet(s)received0.00%packetlossround-tripmin/avg/max=47/68/94msPC>故障背景故障排除IP地址獲取故障DHCP得到錯誤的IP地址故障DHCPRelay故障VRRP故障路由器接口關(guān)閉故障靜態(tài)路由故障主備鏈路故障網(wǎng)絡(luò)優(yōu)化故障-未區(qū)分主備鏈路(1)前面查看路由的時候發(fā)現(xiàn)，CSW1和CSW2上存在等價負載均