Chapter 9 - Managing Routing Through TCP/IP
This chapter discusses the Managing Routing through TCP/IP menu. This menu allows you to configure your server to route packets across an IP network.
From this menu, you can perform the following tasks:
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Manage the default gateway entry ![]()
Manage specific routes ![]()
Manage adjacent networks ![]()
Enable and disable directed broadcasts
Chapter 2 and Chapter 5 contain information on routing IP packets, along with discussions of the default gateway, specific routes, and adjacent networks.
Throughout this chapter, information on the sample Routing Information Worksheet (Figure 9-1 and Figure 9-2) and the sample Adjacent Networks Worksheet (Figure 9-3) is used in examples. These sample worksheets are based on examples from Chapter 5.
Accessing TCP/IP Routing Functions
The Manage Routing through TCP/IP Networks menu allows you to perform all routing management functions. To display this menu, choose Manage Routing through TCP/IP Networks from the TCP/IP main menu.
To route data, IP software needs to know the physical interfaces on your server. If you have not yet defined any interfaces, return to the TCP/IP main menu and use the Manage Interfaces function to do so.
The Manage Routing through TCP/IP Networks menu lists all the physical interfaces defined on the Manage Network Interfaces menu. The menu also displays the default gateway if one has been defined, and shows the status of directed broadcasts for your server.
For each interface, the Manage Routing for TCP/IP menu displays the following information:
Slot - The number of the slot in which the interface's LAN card resides. This field does not apply to the VINES interface.
IP address - The interface's IP address.
Subnetwork mask - The subnetwork mask that was specified for the interface's IP address.
The functions that you can perform from the Manage Routing through TCP/IP Networks menu are described in the sections that follow.
Default Gateway Management Tasks
This section shows you how to manage information for the default gateway. Topics discussed include:
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Specifying the Default Gateway ![]()
Changing the Default Gateway ![]()
Deleting the Default Gateway
Before you change or delete the default gateway, carefully consider whether your action will adversely affect your server's routing capability. For example, deleting the default gateway or specifying a new one could prevent your server from reaching certain destinations.
Specifying the Default Gateway
The steps you perform to specify a default gateway depend on whether the gateway is a VINES server accessible only through VINES:
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If the default gateway is a VINES server accessible only through VINES, use the Manage Routing through VINES Networks menu to add an entry for the server. Refer to Chapter 10 for instructions. ![]()
If the default gateway is a foreign host gateway or a VINES server accessible only through IP, you must either define a direct route to the gateway or specify the interface that connects your server to the gateway. Refer to this chapter for instructions.
To specify the default gateway, perform the following steps:
1. At the Manage Routing through TCP/IP Networks menu, choose SPECIFY/CHANGE Default Gateway.
2. The TCP/IP configuration program asks if the gateway is a VINES server accessed only through VINES. Specify YES or NO.
3. If you specified YES in step 2, you see a list of the servers in your VINES network that were specified through the Manage Routing through VINES Networks function. Choose the appropriate server.
If you specified NO in step 2, the Specify/Change Default Gateway screen appears. Specify the IP address of the foreign host gateway that will act as the default gateway.
When you have completed all steps, the Manage Routing through TCP/IP Networks menu identifies the default gateway, either by the name of the server or by the IP address of the foreign host gateway.
To change the default gateway, choose SPECIFY/CHANGE Default Gateway from the Manage Routing through TCP/IP Networks menu. The configuration program steps you through the same series of screens that are used to specify the default gateway. See the preceding section, "Specifying the Default Gateway," for more information.
To delete the default gateway, perform the following steps:
1. At the Manage Routing through TCP/IP Networks menu, choose DELETE Default Gateway.
2. The configuration program prompts you for confirmation. Specify YES to delete the default gateway, or NO to cancel the deletion. YES is the default.
Specific-Route Management Tasks
This section shows you how to manage specific routes. Topics discussed include:
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Adding a Route ![]()
Modifying a Route ![]()
Deleting a Route
Before you modify or delete a specific route, carefully consider whether your action will adversely affect your server's routing capability. For example, modifying or deleting a route could prevent your server from reaching certain destinations.
The Manage Specific Routes menu allows you to manage all specific routes through gateways. To display the menu, perform the following steps:
1. At the Manage Routing through TCP/IP Networks menu, choose MANAGE Specific Routes.
2. Select the interface for which you are managing specific routes.
The Manage Specific Routes menu lists all the manually created route entries associated with interfaces. It also displays the entry for the default gateway, which cannot be modified from the Manage Specific Routes menu.
The following fields appear for each entry:
Gateway - The IP address of the gateway.
Dest Type - The type of destination. The destination type can be Network (which includes subnetworks) or Host.
Dest IP address - The IP address of the destination. For the default gateway entry, no IP address is shown, since the default gateway does not define a specific route to a destination.
Subnetwork mask - The subnetwork mask for the destination IP address.
Status - The route's status, either in use (the route can be used) or NOT in use (the route is unusable).
The functions available at the Manage Specific Routes menu are described in the sections that follow.
When you add a route, specify the following:
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The IP address of a gateway. ![]()
The IP address of a destination. The destination can be either a network, a subnetwork, or a host. ![]()
The subnetwork mask if the destination is a subnetwork.
Chapter 2 and Chapter 6 provide information about routing.
You can add a route to a network or subnetwork, or to a host. The sections that follow explain both procedures. You should have a completed Routing Information Worksheet on hand before starting these procedures.
Adding a Route to a Network or Subnetwork
To add a route to a network or subnetwork, perform the following steps:
1. At the Manage Specific Routes menu, choose ADD a Route.
2. Enter the IP address of the route's gateway. Using the sample worksheet in Figure 9-1, you would enter 145.179.1.2 for a route to network 147.190.
3. The configuration program asks if the destination you want to specify is a host. Specify NO (the default).
4. At the Specify Destination IP Address screen, enter the IP address of the destination network or subnetwork. Using the sample worksheet, you would specify 147.190 as the destination network that can be reached through 145.179.1.2.
5. At the Specify Subnetwork Mask screen, enter the subnetwork mask if the destination is a subnetwork. Use the default if you specified a non-subnetted network as the destination - for example, 255.255.0.0 for 147.190.
6. The configuration program asks if you want to reach any more destinations through the gateway you specified. In our example, the configuration program would ask if you want to reach any more destinations through 145.179.1.2.
If you answer YES, the Specify Destination IP Address screen appears, allowing you to specify another destination that can be reached through the gateway. Follow the steps in this procedure, beginning at step 3, to add another entry. If you answer NO, the program returns to the Manage Specific Routes menu.
Adding a Route to a Host
Adding a route to a host is similar to adding a route to a network or subnetwork. Perform the following steps:
1. At the Manage Specific Routes menu, choose ADD a Route.
2. Enter the IP address of the route's gateway. Using the sample worksheet in Figure 9-1, you would enter 145.179.1.2 for a route to network 147.190.
The configuration program asks if the destination you want to specify is a host. Specify YES.
3. At the Specify Destination IP Address screen, specify the IP address of the destination host that can be reached through the specified gateway.
The configuration program asks if you want to reach any more destinations through the gateway you specified. Specifying YES enables you to specify another destination. Specifying NO returns you to the Manage Specific Routes menu.
When you have completed all steps, the Manage Specific Routes menu displays the entry you just created, as well as entries that were added previously.
To modify a route, perform the following steps:
1. At the Manage Specific Routes menu, choose MODIFY a Route.
2. Choose the route entry you want to modify. You then can proceed to modify entries on the route configuration screens. The preceding section, "Adding a Route," provides information on these screens.
To delete a route, perform the following steps:
1. At the Manage Specific Routes menu, choose DELETE a Route.
2. Choose the route you wish to delete.
3. The configuration program prompts you for confirmation. Specify YES to delete the entry, or NO to cancel the deletion. YES is the default.
Adjacent Network Management Tasks
An adjacent network is a network that shares a physical interface with your server, but whose hosts have different network IDs from that of your server's interface. For example, suppose your server has an Ethernet interface 135.100.1.1. Through this interface, it can reach all the servers in network 160.134. In the TCP/IP configuration program, you would configure 160.134 as an adjacent network.
The adjacent network management Tasks are:
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Adding an Adjacent Network ![]()
Modifying an Adjacent Network ![]()
Deleting an Adjacent Network
If you must specify routes to adjacent networks or subnetworks, be sure that your Adjacent Networks Worksheet is filled out properly. The worksheet tells you the following for each adjacent network that you have to specify:
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The interface associated with the adjacent network ![]()
The IP address of the adjacent network or subnetwork to which you are creating a route ![]()
The subnetwork mask for the IP address
Before you modify or delete routing information for an adjacent network, carefully consider whether the change will adversely affect your server's routing capability. For example, modifying the IP address of an adjacent network or subnetwork could make it impossible for your server to reach that network or subnetwork.
The Manage Adjacent Networks menu allows you to manage routes to networks and subnetworks that are directly connected to your server by a LAN. To display the menu, perform the following steps:
1. At the Manage Routing through TCP/IP Networks menu, choose MANAGE Adjacent Networks.
2. Choose the interface that connects your server to the network or subnetwork to which you want to define a direct route. The Manage Adjacent Networks menu appears.
The Manage Adjacent Networks menu lists all the manually created routes associated with the selected interface. The following fields appear for each entry:
IP Address - The IP address of the adjacent network or subnetwork.
Subnetwork Mask - The subnetwork mask for the IP address.
Status - The status of the interface, either in use or NOT in use.
The functions that you can perform from this menu are described in the sections that follow.
When you add an adjacent network, you specify the following:
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The IP address of an adjacent network or subnetwork ![]()
The subnetwork mask for the IP address
Perform the following steps, using your Adjacent Networks Worksheet as a guide:
1. At the Manage Adjacent Networks menu, choose ADD an Adjacent Network.
2. At the Configure an Adjacent Network screen, specify the IP address of the network or subnetwork to which you are defining a direct route. Using the sample worksheet in Figure 9-2, you would enter 135.126.2.
3. At the Specify Subnetwork Mask Screen, specify the subnetwork mask if you specified a subnetwork as the destination. Use the default if you specified a network as the destination. For example, 255.255.255.0 would be the default for network 135.126.2.
When you have completed all steps, the Manage Adjacent Networks menu displays the entry for the route you just created, as well as entries that were added previously.
Caution: If you specify an IP network address with no subnetwork mask, routes elsewhere in your network will not be usable if they meet the following criteria:
- They have the same network number as the network you established.
- They use a subnetwork mask.
To modify an adjacent network, perform the following steps:
1. At the Manage Adjacent Networks menu, choose MODIFY an Adjacent Network.
2. Choose the adjacent network you want to modify. The configuration program steps you through the same screens that were used to add the network. The preceding section, "Adding an Adjacent Network," provides information.
Caution: If you specify an IP network address with no subnetwork mask, routes elsewhere in your network will not be usable if they meet the following criteria:
- They have the same network number as the network you established.
- They use a subnetwork mask.
To delete routing information for an adjacent network, follow these steps:
1. At the Manage Adjacent Networks menu, choose DELETE an Adjacent Network.
2. Choose the adjacent network you wish to delete.
3. The configuration program prompts you for confirmation. Specify YES to delete the adjacent network, or NO to cancel the deletion. YES is the default.
Server Management Options for TCP/IP Routing
This section describes the following topics:
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Enabling and Disabling Directed Broadcasts ![]()
Displaying System Routes
Enabling and Disabling Directed Broadcasts
When your server receives a directed broadcast packet that is destined for an attached network (for example, an Ethernet LAN), it automatically broadcasts the packet on the network.
Directed broadcasts are enabled by default. However, situations may arise in which you want to disable directed broadcasts. For example, you may want to stop your server from sending IP broadcasts whenever it receives directed broadcasts from hosts outside your network.
The Manage Routing through TCP/IP Networks menu tells you whether directed broadcasts are enabled or disabled. To change the current setting, perform the following steps:
1. At the Manage Routing through TCP/IP Networks menu, choose ENABLE/DISABLE Directed Broadcasts.
2. The configuration program asks you to confirm your decision. Specify YES or NO. YES is the default. For example, if directed broadcasts were enabled, you would specify YES to disable them, or NO to keep them enabled.
Routes in use include those that the configuration program creates using IP addresses of interfaces and other servers, those created through other means such as ICMP redirect messages, and those created manually. To see a summary of all routes in use, perform the following steps:
1. Select DISPLAY System Routes from the Manage Routing through TCP/IP Networks menu.
2. Select the interface associated with the routes you wish to view.
The next screen displays all the entries for the routes in use. The following information appears for each entry:
Gateway - The IP address of the gateway on the route.
Dest Type - This field provides information about the kind of destination that can be reached by way of the route. The destination can be any one of the following:
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Network - A network or subnetwork. ![]()
Host - A host. ![]()
Direct - An automatically created network or subnetwork route. ![]()
Adjacent - A directly connected network or subnetwork. ![]()
Default - All destinations that can be reached through the default gateway, including networks, subnetworks, and hosts. The default gateway is used when no other routes in use provide a gateway to a destination. Dest IP Address - The IP address of the destination network, subnetwork, or host.
Pkts Fwd - The number of packets forwarded to the destination that can be reached by way of this route.
Sts - The route's status, either UP (the route can be used), or DOWN (the route is unusable).
Flags can be any one of the following:
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Manual - The route was manually defined. ![]()
Automatic - The configuration program defined the route using the IP address assigned to the selected interface. ![]()
Dynamic - The route was created using information from an ICMP redirect packet. ![]()
Modified - The route was created manually or dynamically and was updated based on information from an ICMP redirect packet.