TCP/IP Connections Introduction User Modes Connect Via... Addressing Subnet Masks Config Router Address DNS Search Paths Hosts File 802.3 Saving Configs Troubleshooting Tools For More Info Glossary updated: 8/11/97

"Configure" Option The "Configure" option indicates how an IP address is going to be obtained. The choices available will depend on what was selected in the "connect via" option. Manually Manually means that you received an IP Address from your network administrator and are just going to type it in. This option should always be available, whether you have "MacIP", "Ethernet", "TokenRing" or "PPP" selected, since its always possible to use a static IP address (i.e., one assigned to you and you alone). "Server" options It's possible to have a special kind of server give you an IP address whenever one is needed. Different kinds of servers are available on different types of networks. If "MacIP" is selected in the "Connect Via" popup, you'll have option of "Using MacIP server"; note that you'll also need to select the AppleTalk zone that the MacIP server lives in. It doesn't really matter whose MacIP server you're using (whether Apple IP Gateway or some other device) since they all work pretty much the same: when your Mac needs to initialize the TCP/IP stack when an IP application is first being opened, (or at startup, if you do not have the "load only when needed option" checked), your Mac will do a broadcast in the AppleTalk zone indicated in the TCP/IP panel, basically saying "Hey! I need an IP address. Any MacIP servers out there?" All devices listen to broadcast requests, so any device that is a MacIP server will say to itself "I'm a MacIP server, I can help this guy out" and will send a packet back to the requestor with the appropriate information (such as his IP address and subnet mask). If "Ethernet" or "Token Ring" is selected, you'll see the following type of server options. In each case, the client, i.e., the machine needing an IP address, will send out a broadcast packet on the network; the server recognizes the request, and responds to the client with the appropriate information, such as IP address for the client to use: RARP or Reverse Address Resolution Protocol is used by Sun and other vendors that allows a computer to find out its own IP number, which is one of the protocol parameters typically passed to the client system by DHCP or BOOTP. RARP doesn't support other parameters and using it, a server can only serve a single LAN. DHCP and BOOTP are designed so they can be routed. BOOTP stands for Bootstrap protocol; like RARP, the server administrator needs to configure information that the server will return. Unlike RARP, Bootp supports more informtion than just the IP address, and can be routed across subnets. DHCP, or Dynamic Host Configuration Protocol, is a superset of BOOTP and maintains some backward compatibility. The main difference is that BOOTP was designed for manual pre-configuration of the host information in a server database, while DHCP allows for dynamic allocation of network addresses and configurations to newly attached hosts. Additionally, DHCP allows for recovery and reallocation of network addresses through a leasing mechanism. If "PPP" is selected in "Connect Via" you will also see an option for "PPP Server"; this means that your ISP's PPP server will be sending you your IP address when you connect. In the MacTCP control panel, you had an option for "server" addressing in the "Obtain Address" quandrant of the control panel; if something like "LocalTalk" or "EtherTalk" was selected, it would look for a MacIP server. If Ethernet was selected, it would look for a BootP or RARP server (first one, then, if no answer, the other). DHCP was not supported with MacTCP. MacTCP's option to obtain an address "dynamically" (i.e., at random, something like AppleTalk addressing) was non-standard and could cause problems if an address obtained at random happened to be the address another machine, momentarily offline, was using. This type of addressing is not supported in Open Transport. [Intro |UserModes |ConnectVia |Addressing |Subnet Masks |Config|Routers ]DNS |Search Paths |Hosts File ]802.3 ]Saving Configs ]Troubleshooting ]Tools ]More Info ]Glossary ]