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Appendix B      Concepts   PPP Authentication Protocols
RIP and Enhanced IGRP differ in several ways, as shown in Ta b l e B-1.
Ta b l e B-1 RIP and Enhanced IGRP Comparison
ProtocolIdeal TopologyMetricRouting Updates
RIPSuited for topologies with 
15 or fewer hops.Hop count. Maximum hop 
count is 15. Best route is one 
with lowest hop count.By default, every 30 seconds. 
You can reconfigure this value...

 
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Appendix B      Concepts
  PPP Authentication Protocols
PPP originally emerged as an encapsulation protocol for transporting IP traffic over point-to-point links. 
PPP also established a standard for the assignment and management of IP addresses, asynchronous 
(start/stop) and bit-oriented synchronous encapsulation, network protocol multiplexing, link 
configuration, link quality testing, error detection,...

 
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Appendix B      Concepts
  TACACS+
TACACS+
Cisco 850 and Cisco 870 series routers support the Terminal Access Controller Access Control 
System
 Plus (TACACS+) protocol through Telnet. TACACS+ is a Cisco proprietary authentication 
protocol that provides remote access authentication and related network security services, such as event 
logging. User passwords are administered in a central database rather...

 
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Appendix B      Concepts
  Dial Backup
PVC
A PVC is a connection between remote hosts and routers. A PVC is established for each ATM end node 
with which the router communicates. The characteristics of the PVC that are established when it is 
created are set by the ATM adaptation layer (AAL) and the encapsulation type. An AAL defines the 
conversion of user information into cells. An AAL segments...

 
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Appendix B      Concepts
  NAT
line is up, the backup interface is placed in standby mode. In standby mode, the backup interface is 
effectively shut down until it is enabled. Any route associated with the backup interface does not appear 
in the routing table.
Because the backup interface command is dependent on the router’s identifying that an interface is 
physically down, it is commonly used to back up...

 
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Appendix B      Concepts
  Easy IP (Phase 1)
Translations can be static or dynamic. A static address translation establishes a one-to-one mapping 
between the inside network and the outside domain. Dynamic address translations are defined by 
describing the local addresses to be translated and the pool of addresses from which to allocate outside 
addresses. Allocation occurs in numeric order, and multiple...

 
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Appendix B      Concepts
  QoS
QoS
This section describes Quality of Service (QoS) parameters, including the following:
 IP Precedence
 PPP Fragmentation and Interleaving
 CBWFQ
 RSVP
 Low Latency Queuing
QoS refers to the capability of a network to provide better service to selected network traffic over various 
technologies, including ATM, Ethernet and IEEE 802.1 networks, and IP-routed networks...

 
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Appendix B      Concepts
  QoS
In general, multilink PPP with interleaving is used in conjunction with CBWFQ and RSVP or IP 
Precedence to ensure voice packet delivery. Use multilink PPP with interleaving and CBWFQ to define 
how data is managed; use Resource Reservation Protocol (RSVP) or IP Precedence to give priority to 
voice packets.
CBWFQ
In general, class-based weighted fair queuing (CBWFQ) is used...

 
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Appendix B      Concepts
  Access Lists
Access Lists
With basic standard and static extended access lists, you can approximate session filtering by using the 
established keyword with the permit command. The established keyword filters TCP packets based on 
whether the ACK or RST bits are set. (Set ACK or RST bits indicate that the packet is not the first in the 
session and the packet therefore belongs...

 
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Appendix B      Concepts
  Access Lists