Cisco Router 826 Routers Software Configuration Guide

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Concepts
This chapter contains conceptual information that may be useful to Internet Service Providers or 
Network Administrators when configuring Cisco routers. To review some typical network scenarios, 
refer to “Network Scenarios” in Chapter 2. For information on specific configurations, refer to 
Chapter 3, “Basic Router Configuration” and Chapter 4,...

  
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Overview
The data and voice Cisco 827-4V has four FXS/POTS ports in addition to the 10Base-T Ethernet and 
one ADSL network port, and it supports Voice over IP (VoIP). The four FXS/POTS ports will support 
loop-start functions for connecting to POTS devices up to 500 ft. The Cisco 827-4V router includes a 
digital signal processor (DSP) chip to...

  
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ADSL
ADSL
ADSL is a technology that allows both data and voice to transmit over the same line. It is a packet-based 
network technology that allows high-speed transmission over twisted-pair copper wire on the local loop 
(“last mile”) between a network service provider (NSP) central office and the customer site, or on local 
loops created either...

  
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Routing Protocol Options
is ready to receive data before sending it. When the handshaking is successful, the computers have 
established a connection. IP relies on protocols in other layers to establish the connection if 
connection-oriented services are required. 
IPX exchanges routing information using Routing Information Protocol (RIP), a...

  
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PPP Authentication Protocols
Enhanced IGRP
Enhanced IGRP is an advanced Cisco proprietary distance-vector and link state routing protocol, which 
means it uses a metric more sophisticated than distance (hop count) for route selection. Enhanced IGRP 
uses a metric based on a successor, which is a neighboring router that has a least-cost path to a...

  
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TACACS+
CHAP
CHAP uses a three-way handshake to verify passwords. To illustrate how CHAP works, imagine a 
network topology where a remote office Cisco 827 router is connected to a corporate office Cisco 3600 
router. 
After the PPP link is established, the corporate office router sends a challenge message to the remote 
office router. The remote...

  
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Network Interfaces
Under the Ethernet CSMA/CD media-access process, any host on a CSMA/CD LAN can access the 
network at any time. Before sending data, CSMA/CD hosts listen for traffic on the network. A host 
wanting to send data waits until it detects no traffic before it transmits. Ethernet allows any host on the 
network to transmit whenever...

  
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Dial Backup
Dialer interfaces can be configured independently of any physical interface and applied dynamically as 
needed. 
Dial Backup
Dial backup provides protection against WAN downtime by allowing user to configure a backup modem 
line connection. The following can be used to bring up the dial backup feature in the Cisco IOS software:...

  
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NAT
NAT
Network address translation (NAT) provides a mechanism for a privately addressed network to access 
registered networks, such as the Internet, without requiring a registered subnet address. This mechanism 
eliminates the need for host renumbering and allows the same IP address range to be used in multiple 
intranets.
NAT is configured on...

  
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Easy IP (Phase 2)
Easy IP (Phase 2)
The Easy IP (Phase 2) feature combines Dynamic Host Configuration Protocol (DHCP) server and relay. 
DHCP is a client-server protocol that enables devices on an IP network (the DHCP clients) to request 
configuration information from a DHCP server. DHCP allocates network addresses from a central pool 
on an...