{"id":72,"date":"2008-06-07T14:54:23","date_gmt":"2008-06-07T18:54:23","guid":{"rendered":"http:\/\/www.cchsu.com\/art-en\/?p=72"},"modified":"2008-06-09T01:55:41","modified_gmt":"2008-06-09T05:55:41","slug":"troubleshooting-network-connectivity-3","status":"publish","type":"post","link":"https:\/\/www.cchsu.com\/art-en\/2008\/06\/07\/72\/","title":{"rendered":"Troubleshooting Network Connectivity (3)"},"content":{"rendered":"

The\u00a0TCP\/IP network that most people use today is not really a plug-n-play thing.\u00a0 It\u00a0needs proper configuration.\u00a0 Typically I follow these steps to figure out if the network configuration is correct or not.<\/p>\n

    \n
  1. Do I have an IP address?<\/li>\n
  2. Do I have a working name service?<\/li>\n
  3. Can I reach the machine that I want to connect to?<\/li>\n<\/ol>\n

    The most basic and important part of network configuration is to get a valid IP address.\u00a0 One can simply\u00a0use the ipconfig tool to tell if there is a valid IP address (i.e. something other than 0.0.0.0 or 169.254.*.*).\u00a0 We can further drill down the possible reasons of not having a valid IP address<\/p>\n

      \n
    1. No actual network\u00a0link is established (typically happens in\u00a0wireless network)<\/li>\n
    2. DHCP down<\/li>\n
    3. Misconfiguration<\/li>\n<\/ol>\n

      Wireless devices today typically negotiates well with the wireless router.\u00a0 However, if you want the wireless link to be secure, you’ll need to enable WPA or WPA2, which requires setting up\u00a0passwords to connect to the router.\u00a0 I find that the problems often come from the tools that shipped with wireless routers\/adapters to “help” user setup these configurations.\u00a0 From my personal experience\/bias, these tools creates more problems than the problems that they intend to solve.\u00a0 Here are some rules of thumb that I’d suggest<\/p>\n

        \n
      • Do not install additional programs unless absolutely necessary<\/li>\n
      • If there is a Windows build-in device driver for the wireless adapter, and there is no strong evidence saying that vendor-provided drivers perform better, use the Windows one.\u00a0 It’s not a 3D-graphics card and there’s typically little performance difference between Microsoft and vendor drivers.\u00a0 More than often, you don’t really need the add-on features provided by vendor drivers.<\/li>\n
      • If you can install device driver through Device Manager in Windows, do it that way.\u00a0 I’ve seen too many ill-written setup programs of wireless adapters that\u00a0do lousy jobs and screw the registry.<\/li>\n
      • IMO the best way to do WPA configurations is getting them done through the web interface of router and through the Windows Control Panel.\u00a0 Remember to write down the passwords and settings.<\/li>\n<\/ul>\n

        The criteria that we have an actual network link to the router is that you can ping the router (say, ping 192.168.1.1 and found it’s responsive).\u00a0 Remember to turn off your firewall program when you ping because some firewall can block the ping (ICMP) traffic.<\/p>\n

        DHCP is a nice tool to have, and most routers today have built-in DHCP server.\u00a0 However, if you don’t have a IP address, and the network link is okay (i.e. you can ping the router), I’d then suspect DHCP server is down.\u00a0 A router can still be operational even though its DHCP server is not working, so power cycling the router is typically a worth try.\u00a0 (Just think that the router is a small computer running programs, and DHCP server is one of these programs so it could be dead while other programs running normally.)\u00a0 Again, you’ll need to disable the firewall, do “ipconfig \/renew”, and see if you can acquire an IP address from the DHCP server.<\/p>\n

        One problem that I often see is that people have statically configured their network in the beginning (with some guru’s help), and then purchased new equipments and run the auto-configuration tool.\u00a0 There’s little chance that the auto-configuration tool will respect existing network configuraions and setup accordingly.\u00a0 As a result, you might have some computers configured as 192.168.1.* while others as 192.168.2.*, which by no means will work.<\/p>\n

        The other typical misconfiguration is that people have two routers and try to setup them in a single network segment (i.e. an old wired router as 192.168.1.1 and a new wireless router as 192.168.1.2).\u00a0 You can not have two routers in a single segment.\u00a0 If the numbers of IP address\u00a0really matter, we can play netmask tricks and setup static routes so every device has a 192.168.1.* address, that’s one way to do it.\u00a0 The other way is to downgrade the wireless router to AP or the wired router to hub, so there’s only one router in charge.<\/p>\n

        \u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

        The\u00a0TCP\/IP network that most people use today is not really a plug-n-play thing.\u00a0 It\u00a0needs proper configuration.\u00a0 Typically I follow these steps to figure out if the network configuration is correct or not. Do I have an IP address? Do I have a working name service? Can I reach the machine that I want to connect […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,5,6],"tags":[],"_links":{"self":[{"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/posts\/72"}],"collection":[{"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/comments?post=72"}],"version-history":[{"count":0,"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/posts\/72\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/media?parent=72"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/categories?post=72"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cchsu.com\/art-en\/wp-json\/wp\/v2\/tags?post=72"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}