CCNA: summary doubts

thedude666thedude666 Member Posts: 69 ■■□□□□□□□□
in CCNA & CCENT
Hi all,

I am using the Todd Lammle book for CCNA and I am doubting about the answer on a question about supernetting.
I checked the errata but didn't find anything about this written lab so it might just be me who is doing something wrong :s

Chapter 5.
Written lab.
For each of the following sets of networks, determine the summary address and the mask to be used that will summarize the subnets.
1. 192.168.1.0/24 through 192.168.12.0/24
2. 172.148.0.0/13 through 172.156.0.0/13
3. 192.168.32.0 through 192.168.63.0
4. 203.168.6.0/24 and 203.168.60.0/24
5. 66.66.0.0 through 66.66.15.0
6. 192.168.1.0 through 192.168.120.0
7. 172.16.1.0 through 172.16.7.0
8. 192.168.128.0 through 192.168.190.0
9. 53.60.96.0 through 53.60.127.0
10. 172.16.10.0 through 172.16.63.0

The answers as given in the book:
1. 192.168.0.0/20.
2. 172.144.0.0/16
3. 192.168.32.0 255.255.224.0
4. 192.168.96.0 255.255.240.0
5. 66.66.0.0/16.
6. 192.168.0.0/25
7. 172.16.1.0 255.255.248.0
8. 192.168.128.0 255.255.192.0
9. 53.60.96.0 255.255.224.0
10. 172.16.0.0 255.255.192.0

I will update this body for the answers I would think are correct:
1. 192.168.1.0/24 through 192.168.12.0/24

12 - 1 = 11 => 16subnets necessary => 4bits
192.168.0.0/20

This one seems right

2. 172.148.0.0/13 through 172.156.0.0/13

Boundaries:
172.148.0.0/13 => 3 host bits: steps of 8
128+8 = 136 + 8 = 144
172.144.0.0/13
Range: 172.144.0.0 -> 172.152.255.255

172.156.0.0/13 => 3 host bits: steps of 8
144+8=152 + 8=160
172.152.0.0/13
Range: 172.152.0.0 -> 172.160.255.255

172.144.0.0/10
:s wt* ... the answer in the book is /16. This makes the network even more narrow and it supernetting :s
Is this just me? Am I missing something?

3. 192.168.32.0 through 192.168.63.0

63-32 = 31 => 5 net bits
32+32=64
192.168.32.0/19
Seems ok

4. 203.168.6.0/24 and 203.168.60.0/24

60 - 6 = 54 => 6host bits
203.168.0.0/18

Again wt* :s
Nowhere near the answer from the book :s

5. 66.66.0.0 through 66.66.15.0

15-0 = 15 => 4 net bits
0+16=16

66.66.0.0/20

!!!!!!!!!

6. 192.168.1.0 through 192.168.120.0

120-1=119 => 1 host bits
192.168.0.0/17

7. 172.16.1.0 through 172.16.7.0

7-1=6 => 3 host bits
172.16.0.0/21

8. 192.168.128.0 through 192.168.190.0

190-128 = 62 => 2 host bits
192.168.128.0/18

9. 53.60.96.0 through 53.60.127.0

127-96=31 => 3 host bits (128,64,32)
53.60.96.0/19

10. 172.16.10.0 through 172.16.63.0

63-10 = 53 => 2 host bits
172.16.0.0/18


Sometimes the nets I have as a result do match, however mostly not :s
Anyone can shed a light on this?

It would be very much appreciated!
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Comments

  • EildorEildor Member Posts: 444
    thedude666 wrote: »
    Hi all,

    I am using the Todd Lammle book for CCNA and I am doubting about the answer on a question about supernetting.
    I checked the errata but didn't find anything about this written lab so it might just be me who is doing something wrong :s

    Chapter 5.
    Written lab.
    For each of the following sets of networks, determine the summary address and the mask to be used that will summarize the subnets.
    1. 192.168.1.0/24 through 192.168.12.0/24
    2. 172.148.0.0/13 through 172.156.0.0/13
    3. 192.168.32.0 through 192.168.63.0
    4. 203.168.6.0/24 and 203.168.60.0/24
    5. 66.66.0.0 through 66.66.15.0
    6. 192.168.1.0 through 192.168.120.0
    7. 172.16.1.0 through 172.16.7.0
    8. 192.168.128.0 through 192.168.190.0
    9. 53.60.96.0 through 53.60.127.0
    10. 172.16.10.0 through 172.16.63.0

    The answers as given in the book:
    1. 192.168.0.0/20.
    2. 172.144.0.0/16
    3. 192.168.32.0 255.255.224.0
    4. 192.168.96.0 255.255.240.0
    5. 66.66.0.0/16.
    6. 192.168.0.0/25
    7. 172.16.1.0 255.255.248.0
    8. 192.168.128.0 255.255.192.0
    9. 53.60.96.0 255.255.224.0
    10. 172.16.0.0 255.255.192.0

    I will update this body for the answers I would think are correct:
    1. 192.168.1.0/24 through 192.168.12.0/24

    12 - 1 = 11 => 16subnets necessary => 4bits
    192.168.0.0/20

    This one seems right

    2. 172.148.0.0/13 through 172.156.0.0/13

    Boundaries:
    172.148.0.0/13 => 3 host bits: steps of 8
    128+8 = 136 + 8 = 144
    172.144.0.0/13
    Range: 172.144.0.0 -> 172.152.255.255

    172.156.0.0/13 => 3 host bits: steps of 8
    144+8=152 + 8=160
    172.152.0.0/13
    Range: 172.152.0.0 -> 172.160.255.255

    172.144.0.0/10
    :s wt* ... the answer in the book is /16. This makes the network even more narrow and it supernetting :s
    Is this just me? Am I missing something?

    3. 192.168.32.0 through 192.168.63.0

    63-32 = 31 => 5 net bits
    32+32=64
    192.168.32.0/19
    Seems ok

    4. 203.168.6.0/24 and 203.168.60.0/24

    60 - 6 = 54 => 6host bits
    203.168.0.0/18

    Again wt* :s
    Nowhere near the answer from the book :s

    5. 66.66.0.0 through 66.66.15.0

    15-0 = 15 => 4 net bits
    0+16=16

    66.66.0.0/20

    !!!!!!!!!

    6. 192.168.1.0 through 192.168.120.0

    120-1=119 => 1 host bits
    192.168.0.0/17

    7. 172.16.1.0 through 172.16.7.0

    7-1=6 => 3 host bits
    172.16.0.0/21

    8. 192.168.128.0 through 192.168.190.0

    190-128 = 62 => 2 host bits
    192.168.128.0/18

    9. 53.60.96.0 through 53.60.127.0

    127-96=31 => 3 host bits (128,64,32)
    53.60.96.0/19

    10. 172.16.10.0 through 172.16.63.0

    63-10 = 53 => 2 host bits
    172.16.0.0/18


    Sometimes the nets I have as a result do match, however mostly not :s
    Anyone can shed a light on this?

    It would be very much appreciated!

    Which edition are you reading? Chapter 5 in my book is titled "Managing a Cisco Internetwork".
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  • thedude666thedude666 Member Posts: 69 ■■□□□□□□□□
    Eildor wrote: »
    Which edition are you reading? Chapter 5 in my book is titled "Managing a Cisco Internetwork".

    7th editiion. :) Chapter about subnetting.
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  • Ltat42aLtat42a Member Posts: 587 ■■■□□□□□□□
    Be sure to check the errata page for Todd's book here -
    Wiley: CCNA Cisco Certified Network Associate Study Guide: Exam 640-802, includes CD-ROM, 7th Edition
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  • Todd BurrellTodd Burrell Member Posts: 280
    I completely freaked out after trying these problems in the Lammle book until I reviewed the errata. Most of the answers in the book were wrong - which restored my confidence in my level of understanding for summary routes.
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  • thedude666thedude666 Member Posts: 69 ■■□□□□□□□□
    Seems like this is already discussed: http://www.techexams.net/forums/ccna-ccent/66216-route-summarization.html
    The forum of Lammle have multiple topics about this: Chapter 5: VLSM, Summarization, and Troubleshooting TCP/IP - Lammle Forum

    This even seems to be in the errata. My bad!
    Sybex: CCNA Cisco Certified Network Associate Study Guide: Exam 640-802, includes CD-ROM, 7th Edition
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