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1© 2004, Cisco Systems, Inc. All rights reserved.
CCNA 2 v3.1 Module 8 TCP/IP Suite Error and
Control Messages
222© 2004, Cisco Systems, Inc. All rights reserved.
Purpose of This PowerPoint
• This PowerPoint primarily consists of the Target Indicators (TIs) of this module in CCNA version 3.1.
• It was created to give instructors a PowerPoint to take and modify as their own.
• This PowerPoint is:
NOT a study guide for the module final assessment.
NOT a study guide for the CCNA certification exam.
• Please report any mistakes you find in this PowerPoint by using the Academy Connection Help link.
333© 2004, Cisco Systems, Inc. All rights reserved.
To Locate Instructional Resource Materials on Academy Connection:
• Go to the Community FTP Center to locate materials created by the instructor community
• Go to the Tools section
• Go to the Alpha Preview section
• Go to the Community link under Resources
• See the resources available on the Class home page for classes you are offering
• Search http://www.cisco.com
• Contact your parent academy!
666© 2004, Cisco Systems, Inc. All rights reserved.
Error Reporting and Error Correction
• ICMP is an error-reporting protocol for IP.
777© 2004, Cisco Systems, Inc. All rights reserved.
ICMP Message Delivery
• ICMP messages are encapsulated as data in datagrams in the same way any other data is delivered using IP.
101010© 2004, Cisco Systems, Inc. All rights reserved.
Detecting Excessively Long Routes
• Whether the actual path includes too many hops or a circular routing path exists, the packet will eventually reach the end of its life, known as its time-to-live (TTL).
131313© 2004, Cisco Systems, Inc. All rights reserved.
Code Values for Destination Unreachable Messages
141414© 2004, Cisco Systems, Inc. All rights reserved.
TCP/IP Suite Control Messages
• Control messages are used to inform hosts of conditions such as network congestion or the existence of a better gateway to a remote network.
151515© 2004, Cisco Systems, Inc. All rights reserved.
ICMP Redirect/Change Requests
The default gateway of the host may need to use a redirect/change request to inform the host of the best path to a certain network.
161616© 2004, Cisco Systems, Inc. All rights reserved.
Clock Synchronization and Transit Time Estimation
• The ICMP timestamp request message allows a host to ask for the current time according to the remote host.
• The remote host uses an ICMP timestamp reply message to respond to the request.
171717© 2004, Cisco Systems, Inc. All rights reserved.
Address Mask Requirements
• When a network administrator uses the process of subnetting to divide a major IP address into multiple subnets, a new subnet mask is created.
181818© 2004, Cisco Systems, Inc. All rights reserved.
Router Discovery Message
• When a host on the network boots, and the host has not been manually configured with a default gateway, it can learn of available routers through the process of router discovery.
191919© 2004, Cisco Systems, Inc. All rights reserved.
Router Solicitation Message
• A host generates an ICMP router solicitation message in response to a missing default gateway.
202020© 2004, Cisco Systems, Inc. All rights reserved.
Congestion and Flow Control Messages
ICMP source-quench messages are used to reduce the amount of data lost from congestion.