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Chapter 4 - Planning for Managing IP Interfaces

Introduction

Deciding Which Interfaces Need an IP Address

Ethernet
IBM Token-Ring interface
ProNET-10
The logical VINES interface, which is used only for PCs running the VINES Transport version of PC/TCP

Figure 4-1. Determining Which Interfaces Need IP Addresses

Assigning IP Addresses

Two Ethernet interfaces
An HDLC Server-to-Server interface
A Token-Ring interface

A unique IP address must be assigned to Server 1's VINES interface, since the workstations running the VINES Transport version of PC/TCP are using Server 1 as their default gateway.
Ethernet 1 needs an IP address, so that packets can reach Foreign Host 2.
Ethernet 2 needs an IP address, so that packets can reach Foreign Host 1.

Figure 4-2. Server 1's IP Addresses

Network and Subnetwork Numbers for LAN Interfaces

Figure 4-3. Using Appropriate Network and Subnetwork Numbers

Figure 4-4. Using Inappropriate Network and Subnetwork Numbers

Address Resolution and Broadcast Address Planning

Enable and disable Address Resolution Protocol (ARP) functionality for your server. ARP is enabled by default.

When ARP is disabled, the server does not dynamically resolve IP addresses to physical addresses. The server uses any information that you manually configure on the server to resolve addresses.

You should disable ARP only when no other hosts on a LAN implement ARP. If direct mapping is enabled, ARP is disabled automatically.

Note: When ARP is enabled, direct mapping is not automatically disabled.

Enable and disable direct mapping. This is allowed only for ProNET-10 interfaces.
Create ARP entries for hosts if your server is on a LAN where address resolution cannot be done dynamically. These entries consist of IP address/LAN address pairs.
Implement proxy ARP on your server.

Filling Out the IP Interfaces Worksheet

Server Name - The server to which the information on the worksheet applies.

Interface Name - EtherLink Plus card that provides an interface to Ethernet.

Slot - This is the physical slot number in which the LAN card is installed.

IP Address - The IP address of the interface.

Subnetwork Mask - The subnetwork mask for the IP address. Refer to Table 4-1 if you need help determining the subnetwork mask.

Table 4-1. Subnetwork Masks for Different Address Classes

Broadcast Address - The interface's broadcast address. In most cases, the broadcast address consists of the interface's network/subnetwork number, and all 1s. The VINES interface does not use the broadcast address.

Enabled - Choose Y if you want the IP interface to be enabled immediately when added to the TCP/IP configuration. If you do not want the interface to communicate right away, choose N. The VINES interface is always enabled.

Figure 4-5. Sample IP Interfaces Worksheet

Filling Out the ARP Entries Worksheet

Server Name - The server to which the information on the worksheet applies.

Interface Name - The name that describes the interface for which you are creating ARP entries.

IP Address (Interface) - The IP address of the interface.

Slot - This is the physical slot number in which the LAN card is installed.

ARP Enabled? - Choose Y (the default) if you want to enable ARP. Choose N if you want ARP to be disabled.

Direct Mapping Enabled (ProNET-10 only)? - Choose Y or N to indicate whether you want to enable direct mapping for ProNET-10 LANs. If direct mapping is enabled, ARP is disabled automatically.

IP Address (host) - The IP address of the host on the LAN.

LAN Address - The host's LAN address.

Published? - Choose Y if the entry is published. Choose N if the entry is not published.

Figure 4-6. Sample ARP Entries Worksheet

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