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Internetwork Troubleshooting

Internetwork Troubleshooting. Catalyst 6000 Update Asia PAC - March 2000. 1. © 2000, Cisco Systems, Inc. . © 2000, Cisco Systems, Inc. . Course Agenda. Resources for Troubleshooting Using a Systematic Troubleshooting Method Data-Link Troubleshooting Targets

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Internetwork Troubleshooting

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  1. Internetwork Troubleshooting Catalyst 6000 Update Asia PAC - March 2000 1 © 2000, Cisco Systems, Inc. © 2000, Cisco Systems, Inc.

  2. Course Agenda • Resources for Troubleshooting • Using a Systematic Troubleshooting Method • Data-Link Troubleshooting Targets • Applying Cisco Troubleshooting Tools • Diagnosing and Correcting TCP/IP Problems • Frequency Faced Problems

  3. Resources for Troubleshooting 3

  4. Resources for Troubleshooting • Network Media Test Equipment • Network Monitors • Protocol Analyzers • Network Management Systems • Telephone

  5. Network Media Test Equipment • Cable tester • Near-end Crosstalk (NEXT) • Time Domain Reflectometer (TDR) • Wire Map • Volt-ohm meters • Fiber-optic Cable Testers

  6. Network Management Systems • Fault Management • Accounting Management • Configuration and Name Management • Performance Management • Security Management

  7. Course Agenda • Catalyst 6000 Switch Overview • System Architecture • Configure the Catalyst 6000 Switch • Configure Virtual LANs • Configure ATM LANE Modules • Configure MSFC • Troubleshooting the Catalyst 6000 Switch • Configuration Example Using a Systematic Troubleshooting Method 7

  8. Using a Systematic Troubleshooting Method • Restoring an internetwork that has failed puts incredible pressure no network engineers and network administrator • Use special known expertise and short cuts • requires technical depth and a detailed breadth of knowledge • Unsystematic approach result in wasting time • Documenting helps to capture, preserve, and communicate the experience

  9. Problem Solving Model Finished Define Problem Start Document Facts Gather Facts Consider Possibilities Problem Resolved Create Action Plan yes Implement Action Plan Do Problem Symptoms Stop ? Observe Results no Iterate Process

  10. A Sample Network Problem Network R Network S Host A Host 1 WAN Host 2 Host B Network T Host 3 Host 4

  11. Problem Resolution Finished Define Problem Start Document Facts Gather Facts Consider Possibilities Problem Resolved Create Action Plan yes Implement Action Plan Do Problem Symptoms Stop ? Observe Results no Iterate Process

  12. ATU_R 的基本設定 • 簡單的基本指令 • set • show • set int vip0 ip 10.0.0.1 • set int vip0 mask 255.0.0.0

  13. NAT安裝與設定 • 簡介 • NAT (Network Address Translation) 可以讓你區域網路中的所有機器經由一台通往 Internet 的 server 連線出去，而且只需要註冊該 server一個 IP 就夠了。 • private IP，依照 RFC 1918 規範,預留 private network • 10.0.0.0 - 10.255.255.255/255.0.0.0 • 172.16.0.0 - 172.31.255.255/255.240.0.0 • 192.168.0.0 - 192.168.255.255/255.255.255.0 • 優點:網路設計有彈性,節省ip

  14. NAT安裝與設定 運作原理: 當 packet 要送往網路上時, 所走的途徑是 1-2-3-4-5 當 packet 從網路上傳入時, 所走的途徑是 6-2-3-4-7

  15. 安裝與設定 • OS :FreeBSD,Linux,Solaris… • 在 Kernel File 中加入以下兩個 option, 並重新 make kernel • options IPFIREWALL • options IPDIVERT • 確定 NAT主機上兩張網路卡都有被正常地啟動, 可以透過更改 /etc/rc.conf 來啟動所有的網路卡或是在 /etc/rc.local 手動用 • ifconfig ed1 the_private_ip netmask 255.255.255.0 up (我們假設 ed0 是擁有 public IP 的 interface,而ed1 是對內的 interface)

  16. 安裝與設定 • 確定有 NAT主機會 forward packet, 方法有兩種 • 將 /etc/rc.conf 的 gateway_enable=YES, 或是 • 在 /etc/rc.local 加入或手動執行下面這一行 • sysctl -w net.inet.ip.forwarding=1

  17. 安裝與設定 • 啟動 NAT daemon • 在 /etc/services 加入 (3.0 Release 以後已內建, 可省略) • natd 8668/divert # NAT divert socket • 加入 /etc/rc.local 或手動執行 natd natd -interface ed0 • (此處 ed0 為你擁有 public IP 的 interface)

  18. 安裝與設定 • 最後是設定有關 IPFW 的部份, 首先將 /etc/rc.conf 中的 firewall_enable=YES, 由於我們只是要利用 IPFW 來將 packet 轉往 divert socket, 因此我們不需要複雜的 firewall 設定, 故將原本的 rc.firewall 改名 成 rc.firewall.orig, rc.firewall 只需要下列幾行 • /sbin/ipfw -f flush • /sbin/ipfw add divert natd all from any to any via ed0 • /sbin/ipfw add pass all from any to any

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