CCNA Icnd110 s05l02

© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—5-1
WAN Connections
Enabling the
Internet Connection

Packet Switching

DSL

DSL Service Types Overview

DSL Considerations
Advantages
 Speed
 Simultaneous voice and data transmission
 Incremental additions
 Always-on availability
 Backward compatibility with analog phones
Disadvantages
 Limited availability
 Local phone company requirements
 Security risks

Cable-Based WANs

The Global Internet

Getting an Interface Address from a
DHCP Server
 No manual IP address is configured on the interface.
 The router operates as a DHCP client.
 The ISP provides DHCP information.

Network Address Translation
 An IP address is either local or global.
 Local IP addresses are seen in the inside network.
 Global IP addresses are seen in the outside network.
 Assignment can be static or dynamic.

Port Address Translation

Translating Inside Source Addresses

Overloading an Inside Global Address

Gathering the Required Information

Configuring the Client: Interface and
Connection

Configuring the Client: WAN Wizard

Configuring the Client: Encapsulation

Configuring the Client: IP Addressing

Configuring PAT: Advanced Options

Configuring PAT: Summary

Verifying the DHCP Client Configuration

 Displays active translations
RouterX# show ip nat translation
Pro Inside global Inside local
Outside local Outside global
--- 172.16.131.1 10.10.10.1 ---
---
Displaying Information with show
Commands
RouterX# clear ip nat translation *
 Clears all dynamic address translation entries

Summary
 Packet-switched networks send data packets over different
routes of a shared public network owned by a carrier to reach
the same destination. The route that the packets take to reach
the destination site, however, will vary.
 There are several varieties of DSL, including ADSL, SDSL,
HDSL, IDSL, and CDSL. There are both advantages (speed,
always on, and so on) and disadvantages (availability)
to DSL.
 Cable access to the Internet has become a higher-speed
alternative to DSL and serial.
 The global Internet grew from a U.S. Department of Defense
plan to build a command-and-control network in the 1960s to its
present state as the largest WAN on earth, with multiple ways to
access it and multiple communication, research, and commercial
uses.
 An interface can obtain its IP address from a DHCP server.

Summary (Cont.)
 NAT enables private IP internetworks that use unregistered IP
addresses to connect to the Internet. PAT, a feature of NAT,
enables several internal addresses to be translated to only one or
a few external addresses.
 You can translate your own IP addresses into globally unique IP
addresses when communicating outside of your network.
 Overloading is a form of dynamic NAT that maps multiple
unregistered IP addresses to a single registered IP address
(many-to-one) by using different ports, known also as PAT.
 After NAT is configured, the clear and show commands can be
used to verify that it is operating as expected.

CCNA Icnd110 s05l02

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CCNA Icnd110 s05l02

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