Configuring IP Addressing

Configuring Address Resolution Methods

Configuring Local-Area Mobility

Local-area mobility provides the ability to relocate IP hosts within a limited area without reassigning host IP addresses and without changes to the host software. Local-area mobility is supported on Ethernet, Token Ring, and FDDI interfaces only.

To create a mobility area with only one router, use the following commands in the interface configuration mode:

 

Command

 

 

Purpose

Step 1

 

 

 

 

Router(config-if)# interface

type number

 

Enters interface configuration mode.

Step 2

 

 

 

 

Router(config-if)# ip mobile

arp [timers

keepalive

Enables local-area mobility.

 

hold-time][access-groupaccess-list-number name]

 

 

 

 

 

 

To create larger mobility areas, you must first redistribute the mobile routes into your Interior Gateway Protocol (IGP). The IGP must support host routes. You can use Enhanced Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), IS-IS, or RIPv2. To redistribute the mobile routes into your existing IGP configuration, use the following commands in configuration mode:

 

Command

 

Purpose

Step 1

 

 

Router(config)# router {eigrp autonomous-system

Enters router configuration mode.

 

isis [tag] ospf process-id

rip}

 

Step 2

 

 

 

Router(config)# default-metric

number

Sets default metric values.

 

or

 

 

 

Router(config)# default-metric

bandwidth delay

 

 

reliability loading mtu

 

 

Step 3

 

 

Router(config)# redistribute mobile

Redistributes the mobile routes.

 

 

 

 

Mobile routes will always be preferred over a subnet boundary or summarized route because they are more specific. It is important to ensure that configured or redistributed static routes do not include any host routes for the potentially mobile hosts; otherwise, a longest match could come up with two routes and cause ambiguity. Mobile routes will be seen as external routes to the configured routing protocol, even within a summarization area; therefore, they will not be properly summarized by default. This is the case even when these routes are advertised at a summarization boundary, if mobile hosts are not on their home subnet.

Mapping Host Names to IP Addresses

Each unique IP address can have an associated host name. The Cisco IOS software maintains a cache of host name-to-address mappings for use by the connect, telnet, and ping EXEC commands, and related Telnet support operations. This cache speeds the process of converting names to addresses.

IP defines a naming scheme that allows a device to be identified by its location in the IP. This is a hierarchical naming scheme that provides for domains. Domain names are pieced together with periods

(.)as the delimiting characters. For example, Cisco is a commercial organization that the IP identifies by a com domain name, so its domain name is cisco.com. A specific device in this domain, the File Transfer Protocol (FTP) system, for example, is identified as ftp.cisco.com.

Cisco IOS IP Configuration Guide

IPC-15

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Cisco Systems 78-11741-02 manual Mapping Host Names to IP Addresses, Configuring Local-Area Mobility, IPC-15