TOPIC
This article tells how to troubleshoot difficulties with TCP/IP connections on a Macintosh computer.
DISCUSSION
Whenever clients report difficulties accessing IP services, it is good practice to verify IP connectivity at the client and at the server. Even if the client connected successfully in the past, many different things could cause unsuccessful attempts at any time, such as: Testing IP connectivity is often done using utilities that send ping packets. Ping packets are simply small packets from one host to another, that request a response from the recipient. Many ping utilities are available for free download on the Internet. One favorite is MacTCP Watcher. A ping utility is invaluable when troubleshooting IP connections, and the following suggestions are assuming that some ping utility is available. If no ping utility is available, then use whatever IP applications are at hand; the simpler the better. Remember that the device you are attempting to contact has to support the service that the client software is trying to reach. You may be able to use a Web browser to test a connection with another Macintosh that has Personal Web Sharing enabled, but you cannot use it to test a connection to your router. Here is a suggested troubleshooting path for isolating difficulties with a client trying to connect to the host. Ping the host using its Domain name If pinging succeeds, then there is no fault with the client or the IP connection between client and host. Your next step would be to check the applications at client and host, and look for faults there (Web server, file server, mail client, and so forth). If pinging fails, it could indicate a fault with the routers or DNS servers, not necessarily with the workstation itself. Go on to the next step. Ping device on local subnet using IP address Pinging a device on your same subnet using its IP address does not require routers or DNS servers to be successful, so it verifies that each device is able to communicate, at least on its own subnet, using TCP/IP. Important: be sure that the workstation you are attempting to ping has its IP stack (protocol set) initialized. Most Macintosh computers do not initialize the IP stack until an application that uses IP is opened. On the Macintosh you'll be pinging, open an IP application, such as the Web browser or a ping utility, to initialize the stack before attempting the ping. You can determine which other devices are on the same subnet by checking the physical connections (are they connected to the same hub? or same bus?) or by checking their IP addresses (are the network portions of the IP addresses identical? You have to consider the IP address AND the subnet mask to determine this). - Check network connections: The workstation's TCP/IP panel may be configured with a router address. (This should be the router port which is on the same subnet as the workstation itself.) All communications with devices not on the same subnet as the workstation must pass through this router, so if it is not available, your client will not be able to talk to anyone outside the subnet. Ping DNS server Whenever a host attempts to make a connection using a domain name, that name must first be resolved to an IP address. The name is sent to the first DNS server listed in the TCP/IP control, and if that server does not respond, it will be sent to the second, the third, and so on. Try pinging the DNS servers listed. |
Document Information | |
Product Area: | Communications-Networking |
Category: | Network Management |
Sub Category: | General Topics |
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