Accessing the WAN, CCNA Exploration Companion Guide
First Edition
Copyright © 2008 Cisco Systems, Inc.
ISBN-10: 1-58713-205-2
ISBN-13: 978-1-58713-205-6
Warning and Disclaimer
Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information provided is on an "as is" basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the CD or programs accompanying it.
When reviewing corrections, always check the print number of your book. Corrections are made to printed books with each subsequent printing.
First Printing: April 2008
Corrections for August 24, 2012
Pg / Error / Correction393 / Chapter 6, first paragraph last sentence
Reads:
Adding users does not impede performance, unless the DSLA Internet connection to the ISP, or the Internet, becomes saturated. / Should read:
Adding users may slightly impede performance. As well DSL performance could be impeded if they DSLAM internet connection to the ISP, or the Internet, becomes saturated.
Corrections for October 7, 2010
333 / Chapter 5, Figure 5-15, fourth example in figure
Reads:
Ignore Last Four Address Bits / Should read:
Ignore First Six Address Bits
373 / Chapter 5, Question 14, Answer D
Reads:
D. Permits/denies only entire protocols based on network address / Should read:
D. Permits/denies entire protocol suite based on a network address
391 / Chapter 6, Figure 6-8
Reads:
1KHz / Should read:
1 MHz
419 / Chapter 3, Question 2
Reads:
When accommodating a teleworker, which type of connection should be used when mobile access during traveling is required and broadband options are available? / Should read:
When accommodating a remote teleworker, which type of connection should be used when broadband options are not available?
470 / Chapter 7, Table 7-5
Remove steps 2 & 3 / Renumber steps
Where 4 become 2, 5 become 3, 6 becomes 4, 7 becomes 5
568 / Chapter 8, Table 8-10, fourth line down, second column
Reads:
UP to 48 kbps / Should read:
Up to 64 kbps
605 / Appendix, number 20. X.25, first bullet
Reads:
§ An older, low-capacity WAN technology with a maximum speed of 48 kbps. Typically used in dialup mode with point-of-sale card readers to validate transactions on a central computer. / Should read:
§ An older, low-capacity WAN technology with a typical speed of 64 kbps. Typically used in dialup mode with point-of-sale card readers to validate transactions on a central computer.
Corrections for April 5, 2010
Pg / Error / Correction68 / Chapter 2, Figure 2-13
Table reads:
Connector 1 Connector 2 Function
2 2 Rx<-Tx
3 3 Rx->Tx
5 5 Signal ground / Should read:
Connector 1 Connector 2 Function
2 3 Rx<-Tx
3 2 Rx->Tx
5 5 Signal ground
76 / Chapter 2, Paragraph beginning after Step 2, second configuration:
Reads:
R1(config-router)# encapsulation hdlc / Should read:
R1(config-if) encapsulation hdlc
90 / Chapter 2, Figure 2-28 Establishing the Link, Key below figure:
Reads:
à
LCP Message Exchange
ß
- - >
NCP Message Exchange
<- - / Should read:
- - >
LCP Message Exchange
- - >
ß
NCP Message Exchange
ß
96 / Chapter 2, Figure 2-33 NCP Process, Key below figure:
Reads:
à
LCP Message Exchange
ß
- - >
NCP Message Exchange
<- - / Should read:
- - >
LCP Message Exchange
- ->
ß
NCP Message Exchange
ß
167 / Chapter 3, Frame Relay, first and second bullet points and last two paragraphs
Reads:
· The BECN bit, indicated by the B’s in Figure 3-30, is set on every frame that the switch receives on the congested link.
· The FECN bit, indicated by an F in Figure 3-29, is set on every frame that the switch places on the congested link.
DTEs receiving frames with the ECN bits set are expected to try to reduce the flow of frames until the congestion clears.
To summarize, Figure 3-28 shows that while switch A is putting a large frame on interface 1, other frames for this interface are queued. In Figure 3-29, the Frame Relay switch setting the FECN bit warns the downstream devices about the queue. In Figure 3-30, the Frame Relay switch setting the BECN bit warns that upstream devices about the queue – even though they may not have contributed to the congestion. / Should read:
· The FECN bit, indicated by F in Figure 3-29, is set on every frame that the switch receives on the congested link.
· The BECN bit, indicated by B in Figure 3-30, is set on every frame forwarded to the downstream sending switches.
To summarize, Figure 3-28 shows that while switch A is putting a large frame on interface 1, other frames for this interface are queued causing congestion. In Figure 3-29, switch A sets the FECN bit on frames forwarded to the upstream destination switch to warn them about the congested queue. In Figure 3-30, switch A sets the BECN bit to inform the downstream sending devices about the congested queue – even though they may not have contributed to the congestion.
DTEs receiving frames with the BECN bit set are expected to try to reduce the flow of frames until the congestion clears.
419 thru 427 / Running Header
Reads: Chapter 3: Application Layer Functionality and Protocols / Should read:
Chapter 6: Teleworker Services
This errata sheet is intended to provide updated technical information. Spelling and grammar misprints are updated during the reprint process, but are not listed on this errata sheet.
Updated 08/24/2012