Subnetting question... CCNA

[jsingh7]

I have a Subnetting question... I can answer ALL questions in the Sybex book... the 5 basic questions... # of Subnets, # Hosts, Valid Subnets, Valid Hosts, Broadcast Address...

So, I tried a question from the Sybex Flashcards... I don't get it... neither the question, nor the answer... can someone explain... in detail if possible...

Q: What is the Subnet Broadcast Address for the following... 172.16.10.30 255.255.255.128

Answer: 172.16.30.127

 

[Sigocpt]

That looks like an error/misprint on the cards.

The answer is : 172.16.10.127

Sigocpt

 

[jsingh7]

Yea, that is what I thought the answer was. I really like the Sybex CCNA book and simulator, but there are SO MANY mistakes in the book it's not even funny. Does anyone know if Todd Lammle has come up with a document that atleast points out the mistakes? I'm almost done with the book, and have been practicing a lot, but I'm afraid I will miss a few questions due to the mistakes in the book.

Also, does anyone have any tips for the 640-607 exam as compared to the older 640-507 exam? I know it's the same material but worded differently, with more concentration on commands...but can someone give me some examples, etc.... Thanks.

J. Singh

 

[CCIEWANNABE]

IP Address: 172.16.10.30
Address Class: B = 10nnnnnn.nnnnnnnn or 16 bits or two occtets
Network Address : 172.16.0.0

Subnet Address: 172.16.10.0
Subnet Mask : 255.255.255.128 10nnnnnn.nnnnnnnn
Subnet bit mask: 10nnnnnn.nnnnnnnn.ssssssss.shhhhhhh
Subnet Bits: 25 = 10nnnnnn.nnnnnnnn.ssssssss.s
Host Bits: 7 = hhhhhhh
Possible Number of Subnets: 512
Hosts per Subnet: 126

10nnnnnn.nnnnnnnn = network class “B” equals 16 bits
ssssssss.s = subnet bits Class “B” Eights bits and One additional bit of new Octet which now equals 9 bits plus the Class B value of 16. Totals bits 16 + 9 = 25 bits for subnet values.

hhhhhhh equals values available for host assignments.
1111111 is all ones. Watch the colors assignments:
Broadcast: 172.16.10.127
10101100.00010000. 00001010.0 1111111
10101100.00010000.00001010.0 1111111

One Octect equals 8 bits Four Octets in IPv4
Broadcast: 172.16.10.127 Route once; switch many

 

[epohl]

This page contains corrections to the errors in the book.

http://www.sybex.com/erratatracking.nsf/weberrataform?OpenForm&ISBN=2647