Copyright (C) 1997, 1998 by International Business Machines Corporation

# TCP/IP Configuration Notebook Online Help

## Routing Tab

Use this tab to add, change, or delete routing table entries. A routing table entry consists of the following information:

- Route type

- Destination address

- Router address

- Metric count

- Subnet mask

To use your computer as a router, check the IP Forwarding box on the Routing tab.

The routing table information is saved in your SETUP.CMD file.

The selections on this page are:

Route Type... list box
  Contains your network, host, and default routing table entries, which are saved in the SETUP.CMD file.

  If you plan to simultaneously use TCP/IP through a LAN connection and the Internet Connection Kit through a service provider, you must define the net route to your LAN. (A "net" route is one of several route types, the others being "host," and "default.")

  In this case, the net route specifies the internet address of the LAN you want to access while simultaneously connected to the Internet. Once you have established a route to your network, you can access all hosts on that network.

  To have TCP/IP calculate the net route for you, click the Create Default Net Route for a Given Host push button. (This is a "net" route to be used by default, not to be mistaken for a "default" route.)

  Note: To create this net route you must already have a default route configured and added to the Route Type... list box (or routing table) on the Routing tab; this is what enables the Create Default Net Route... push button. The TCP/IP Configuration Notebook uses the default route address to construct a working "net" route for you automatically.

  Adding this alternate net route is necessary because the default route you would normally use to connect to other computers on your LAN is ignored by Internet service providers. They use their own default, and only one default route can be active at a time.

IP Forwarding

  To use your computer as an IP router, check the IP Forwarding box.

  You can also use the IPGATE command to enable or disable IP forwarding.

  At installation time, IP forwarding is disabled (the check box is not checked). This is the default.

The push buttons on this page are:

Create Default Net Route for a Given Host

  Request that TCP/IP calculate the route to a network on which a specific host resides. Once a route to a network has been established, you can access all hosts on that network.

  Note: To do this you must have a "default" route type configured and added to the Route Type... list box; this is what enables the Create Default Net Route... push button. The TCP/IP Configuration Notebook uses this default route addressing to construct a working net route for you automatically.

  When you click this push button, the Create Default Net Route window appears.

  The fields on this window are:

  IP Address or Host Name of the Computer You Are Trying to Connect To

    Specify the IP address or host name of the computer you want to access. For example, 198.86.40.81 or SUNSITE.UNC.EDU.

    Note:

    > It is recommended you use the IP address, if known. If you specify a host name that cannot be resolved, an error message displays. You will then need to specify the IP address.

  Additional push buttons are:

  OK
    Close the window and save any changes.

  Cancel
    Close the window and discard any changes.

  Help
    Get help information for this notebook page.

Add
  Insert a routing table entry into the list box. When you select the Add push button, the Route Entry window appears.

  The fields on this window are:

  After/Before Current List Selection radio buttons

    Select a radio button to add the new entry either after or before the current entry in the Route Type... list box on the Routing tab.

  Route Type

    Select one of the following route types to define a route:

    Net
      Specifies that a network-specific route is to be added. With a net route, the destination address is the internet address of a particular network. A datagram destined for that host is routed through the router using the internet address of the router, unless a host route also applies to the datagram's destination host address. When a conflict between a host and net route occurs, the host route is used.

    Host
      Specifies that a host-specific destination is to be added. With a host route, the destination address is the internet address of a particular host. A datagram destined for that host is routed through the router using the router address as the internet address.

    Default
      Specifies all destinations not defined with another routing table entry. With a default route, the destination address is all zeros (0s). If no host or net routes apply to a datagram's destination host address, the datagram is routed through the default router using the internet address given by the router address.

  Destination Address

    Specify the internet protocol (IP) address of the destination host, network, or subnet. The IP address must be in 32-bit dotted-decimal notation.

    This field is required for all route types except Default. If the route type is Default, this field is not active.

  Router Address

    Specify the internet protocol (IP) address of the next hop in the path to the destination. This field is required.

    The IP address must be in 32-bit dotted-decimal notation.

  Metric Count

    Specify a number between 1 and 15, inclusive, to indicate the number of hops to the destination.

    A value of 16 or greater indicates that the network cannot be reached. This field is required.

  Subnet Mask

    LAN interfaces can use different subnet masks, giving you the capability of adding routes by specifying a subnet mask (variable subnet routes).

    Specify a subnet mask when adding a route. If you do not specify a subnet mask, the stack selects one for you, but the result may not be your preference.

    Specify the subnet mask in 32-bit dotted-decimal notation.

  Additional push buttons are:

  OK
    Close the window and save any changes.

  Cancel
    Close the window and discard any changes.

  Help
    Get help information for this notebook page.

Change
  Modify a routing table entry selected from the list box. When you select the Change push button, the Route Entry window appears.

  The fields you can change from this window are:

  Route Type

    Select one of the following route types to define a route:

    Net
      Specifies that a network route is to be added.

    Host
      Specifies that a host destination is to be added.

    Default
      Specifies all destinations not defined with another routing table entry.

  Destination Address

    Specify the internet protocol (IP) address of the destination host, network, or subnet. The IP address must be in 32-bit dotted-decimal notation.

    This field is required for all route types except Default. If the route type is Default, this field is not active.

  Router Address

    Specify the internet protocol (IP) address of the next hop in the path to the destination. This field is required.

    The IP address must be in 32-bit dotted-decimal notation.

  Metric Count

    Specify a number between 1 and 15, inclusive, to indicate the number of hops to the destination.

    A value of 16 or greater indicates that the network cannot be reached. This field is required.

  Subnet Mask

    LAN interfaces can use different subnet masks, giving you the capability of adding routes by specifying a subnet mask (variable subnet routes).

    Specify a subnet mask when adding a route. If you do not specify a subnet mask, the stack selects one for you, but the result may not be your preference.

    Specify the subnet mask in 32-bit dotted-decimal notation.

  Additional push buttons are:

  OK
    Close the window and save any changes.

  Cancel
    Close the window and discard any changes.

  Help
    Get help information for this notebook page.

Delete
  Erase the list box entry you selected, which will be displayed in a Delete window. You cannot modify the displayed entry; click OK to delete it, or Cancel to close the window without deleting.

Undo
  Remove any changes made since you last accessed this page.

OK
  Close the TCP/IP Configuration Notebook and save all changes made since opening it.

Cancel
  Close the TCP/IP Configuration Notebook and discard any changes made since opening it.

Help
  Get help information for this notebook page.

How Do I?

For a step-by-step description of key tasks you can do from this page, go to:

- Configuring Routing Information

- Adding a Routing Table Entry

- Changing a Routing Table Entry

- Deleting a Routing Table Entry

[ Top of Page | Previous Page | Next Page | Table of Contents ]