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Chapter 8 - Managing IP Interfaces and ARP Entries

Introduction

Assign IP addresses to either a physical LAN interface or the logical VINES interface. The IP Interfaces Worksheet, discussed in Chapter 4, tells which interfaces you have to add, and the parameters they require.
Establish Address Resolution Protocol (ARP) dialogues with other machines in your network that implement ARP. The ARP Entries Worksheet, also discussed in Chapter 4, tells which interfaces require you to create ARP entries, or to enable or disable ARP.

Worksheets

Figure 8-1. Sample IP Interfaces Worksheet

Figure 8-2. Sample ARP Entries Worksheet

Accessing IP Interface Management Functions

Interface - The name of the interface.

St - The interface's status. This field displays E if the interface is enabled, D if the interface was manually disabled, or SD if the system tried unsuccessfully to enable the interface (that is, if the interface was disabled because of a system failure, or if the server could not find the LAN card when it was booted). If defined, the VINES interface is always enabled.

Slt - 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 IP address assigned to the interface.

Subnetwork mask - The subnetwork mask specified for the interface's IP address.

Broadcast addr - The broadcast/destination address of the interface, which is used to send broadcasts over the attached physical medium. Typically, the address consists of the network and subnetwork number (if subnetting is used) in the IP address of the interface, and a host field in which the bits are either all zeros or all ones. This field does not apply to the VINES interface.

Interface Management Tasks

Adding an IP interface
Modifying an IP interface
Deleting an IP Interface

Adding an Interface

1. Choose ADD an interface.

2. At the next menu, choose a LAN card or the VINES interface.

Note: The VINES interface is available only if the Banyan Routing option is installed on your server.

3. If you choose the VINES interface, the configuration program prompts you to confirm your decision. You should choose the VINES interface only if workstations use VINES to route IP traffic to your server. These workstations need the VINES Transport version of FTP Software, Inc.'s PC/TCP. Choose YES to continue. Choose NO to cancel the addition.

4. At the IP Interface Address screen, assign an IP address to the selected interface. Using the sample worksheet in Figure 8-1, you would assign 160.134.1.1 to the first EtherLink interface.

5. At the Specify Subnetwork Mask screen, specify the subnetwork mask for the IP address. Use the default if the IP address is not subnetted. Using the sample worksheet, you would specify 255.255.255.0 for the IP address you assigned to the first EtherLink interface.

6. At the next screen, specify whether you want the interface to be enabled. YES is the default.

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.

Modifying an Interface

1. At the Manage Network Interfaces menu, choose Modify an Interface.

2. Choose the interface you wish to modify. You then display the screens containing interface information. See the preceding section, "Adding an Interface," if you need information.

3. Modify the interface information.

4. After modifying information, return to the Manage Network Interfaces menu, which shows the new information you have entered for the interface.

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.

Deleting an Interface

Note: Deleting an IP interface removes the interface, as well as the ARP entries, adjacent networks, and routing entries associated with it, from the TCP/IP configuration.

1. At the Manage Network Interfaces menu, choose DELETE an Interface.

2. Choose the interface you wish to delete.

3. The configuration program prompts you for confirmation. Specify YES to delete the interface, or NO to cancel the deletion. YES is the default.

Enabling and Disabling an Interface

1. At the Manage Network Interfaces menu, choose ENABLE/DISABLE an interface.

2. Choose an interface from the list on the screen.

3. The configuration program asks you to confirm your decision. Specify YES or NO. (YES is the default.) For example, if the interface is enabled, specify YES to disable the interface, or NO to keep the interface enabled.

Note: If you disable an interface, any routes, ARP entries, and adjacent networks configured for that interface will be deleted by the system.

Changing an IP Broadcast Address

1. At the Manage Network Interfaces menu, choose CHANGE Broadcast Address.

2. Choose the interface for which you are changing the IP broadcast address.

3. At the next screen, enter the new IP broadcast address.

Address Resolution Protocol Management Tasks

The Manage ARP Entries Menu
Adding an Entry
Modifying an Entry
Deleting an Entry
Displaying System ARP Entries
Enabling and Disabling ARP
Enabling and Disabling Direct Mapping

1. At the Manage Network Interfaces menu, choose MANAGE ARP Entries.

2. Select the LAN interface for which you are managing ARP entries.

IP Address - The IP address of the host.

LAN Address - The LAN address of the host.

Type - The entry type: Permanent (manually configured) or, if the entry is both permanent and published, perm/publish.

Status - The status of the entry: in use if the interface is enabled, or NOT in use.

Adding an ARP Entry

1. At the Manage ARP Entries menu, choose ADD an Entry.

2. At the CONFIGURE an ARP Entry screen, specify the IP address of a host on the LAN and its LAN address. Using the sample worksheet in Figure 8-2, you would assign 160.134.2.2 as the IP address and 02608c313416 as the LAN address for a host on Ethernet.

3. At the next screen, the configuration program asks whether the entry should be published. Specify NO (the default) to make the entry permanent. Specify YES to make the entry both permanent and published. Also, specify YES if your server is implementing proxy ARP.

4. When you complete all steps, the Manage ARP Entries menu appears. It displays the ARP entry you just created, as well as entries that were added previously.

Modifying an ARP Entry

1. At the Manage ARP Entries menu, choose MODIFY an Entry.

2. Choose the entry you wish to modify. Display the screens that contain information on the entry, and modify the information accordingly. See the preceding section, "Adding an ARP Entry," for more information.

3. After modifying the information, return to the Manage ARP Entries menu. The menu shows the new information you entered.

Displaying System ARP Entries

IP Address - The IP address of a destination reachable from this server through IP.

Link Address - The physical LAN address of the destination.

Status Flags - The status of the ARP transaction. Table 8-1 summarizes the status flags field.

Table 8-1. ARP Status Flags

Deleting an ARP Entry

1. At the Manage ARP Entries menu, choose DELETE an Entry.

2. Choose the entry.

3. The configuration program prompts you for confirmation. Specify YES if you want to delete the entry, or NO if you want to cancel the deletion. YES is the default.

Enabling and Disabling ARP

Many of the hosts to which your server is connected on a LAN do not support ARP. You want to disable ARP to stop unnecessary traffic.
ARP does not correctly match IP addresses and LAN addresses. You want to disable ARP and begin troubleshooting the problem.

1. At the Manage ARP Entries menu, choose ENABLE/DISABLE ARP.

2. The configuration program asks you to confirm your decision to enable or disable ARP. Specify YES or NO. YES is the default. For example, if ARP is enabled, specify YES to disable it, or NO to keep it enabled.

Caution: Disabling Direct Mapping does not enable ARP automatically.

Enabling and Disabling Direct Mapping

1. At the Manage ARP Entries menu, choose ENABLE/DISABLE Direct Mapping.

2. The configuration program asks you to confirm your decision. Specify YES or NO. YES is the default. For example, if direct mapping is enabled, specify YES to disable it, or NO to keep it enabled.

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