Question from ccna intro

Seems to wrong to me, checked update on this one... since it's subnetting I am sure I am doing something wrong.
I came up with... and ruled out B as an answer
Subnet 10.4.4.0
First 10.4.4.1
Last 10.4.7.254
Broad 10.4.7.255

So I see no answer... any input

The correct answer(s): B The figure shows an internetwork, with IP addresses and default gateways shown for some devices.

The addresses have been configured on the routers, and the PCs have been configured using the same subnet masks as the routers on the LANs. A routing protocol has been enabled, and both routers have learned all routes known by the other router. Which of the following statements is true regarding the behavior of IP in this network?

A.) The R1 LAN subnet supports more than 1100 host addresses.
B.) A new PC added to the R1 LAN could be assigned IP address 10.5.0.0/23, default gateway 10.4.4.200, and be able to ping PC3.
C.) The R1 LAN subnet supports exactly 254 host addresses.
D.) A new PC added to the R1 LAN could be assigned IP address 10.6.1.1/23, default gateway 10.4.4.200, and be able to ping PC3. The R1 LAN subnet uses a prefix of /23, which implies a mask of 255.255.254.0, and 9 host bits.

The formula for the number of hosts in a subnet is 2^9, minus 2, or a total of 510 hosts. The R1 LAN has a subnet number of 10.4.0.0, a range of valid addresses of 10.4.0.1 through 10.5.255.254, with a subnet broadcast address of 10.5.255.255. Note that odd-looking addresses 10.4.4.255 and 10.5.0.0 are inside the range of valid IP addresses.

PC1

R1
10.4.4.4/23 10.4.4.200/23

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Comments

georgemc

Daniel333 wrote:

Seems to wrong to me, checked update on this one... since it's subnetting I am sure I am doing something wrong.
I came up with... and ruled out B as an answer
Subnet 10.4.4.0
First 10.4.4.1
Last 10.4.7.254
Broad 10.4.7.255

So I see no answer... any input

The correct answer(s): B The figure shows an internetwork, with IP addresses and default gateways shown for some devices.

The addresses have been configured on the routers, and the PCs have been configured using the same subnet masks as the routers on the LANs. A routing protocol has been enabled, and both routers have learned all routes known by the other router. Which of the following statements is true regarding the behavior of IP in this network?

A.) The R1 LAN subnet supports more than 1100 host addresses.

We know A is wrong because with a subnet mask of /23 or 255.255.254.0 we have nine bits for hosts. 2^9-2=510 valid hosts.

B.) A new PC added to the R1 LAN could be assigned IP address 10.5.0.0/23, default
gateway 10.4.4.200, and be able to ping PC3.

From the addresses and mask given in the diagram below we know our range is
10.4.4.0 - 10.4.5.255 for a total of 512-2=510 valid host addresses.
The address for the new PC fits in this range just fine, making B the only correct answer of the four choices given.

10.4.0.0 - 10.4.1.255 is a separate subnet with 510 valid host addresses.

10.4.2.0 - 10.4.3.255 is a separate subnet with 510 valid host addresses.

C.) The R1 LAN subnet supports exactly 254 host addresses.

We know this is wrong from the explanations above.

D.) A new PC added to the R1 LAN could be assigned IP address 10.6.1.1/23, default gateway 10.4.4.200, and be able to ping PC3. The R1 LAN subnet uses a prefix of /23, which implies a mask of 255.255.254.0, and 9 host bits.

We know this is wrong because 10.6.1.1 falls outside of our valid range.

The formula for the number of hosts in a subnet is 2^9, minus 2, or a total of 510 hosts. The R1 LAN has a subnet number of 10.4.0.0, a range of valid addresses of 10.4.0.1 through 10.5.255.254, with a subnet broadcast address of 10.5.255.255. Note that odd-looking addresses 10.4.4.255 and 10.5.0.0 are inside the range of valid IP addresses.

Is this your input or text from the explanation of the question? It doesn't seem to match up with the diagram below?

PC1
R1
10.4.4.4/23 10.4.4.200/23

Hope this helps...

Georgemc

Daniel333

Alright, I guess I missing something here. How is that in a subnet?

I seriously don't see how an address with 10.5.x.x can't possibly in that subnet...
10.4.4.200/23

Subnet 10.4.4.0
First 10.4.4.1
Last 10.4.7.254
Broad 10.4.7.255

So if you add a note with an address of 10.5.x.x /23.. it won't work there, right?

georgemc

Daniel333 wrote:

Subnet 10.4.4.0
First 10.4.4.1
Last 10.4.7.254
Broad 10.4.7.255

This info is wrong in relation to this question.

The correct info for this question is
Subnet 10.4.4.0
First 10.4.4.1
Last 10.4.5.254
Broad 10.4.5.255

Daniel333 wrote:

So if you add a node with an address of 10.5.x.x /23.. it won't work there, right?

georgemc wrote:

10.4.4.0 - 10.4.5.255 for a total of 512-2=510 valid host addresses.
The address for the new PC fits in this range just fine, making B the only correct answer of the four choices given.

AAhhh! you're right. It must be way to late to be doing this. My math was right but for some reason I was seeing what I believed they meant (10.4.5.0 /23) instead of what was actually written (10.5.0.0).

NONE OF THE GIVEN DISTRACTORS ARE CORRECT!

Which book is this from

georgemc

daniel333 wrote:

The formula for the number of hosts in a subnet is 2^9, minus 2, or a total of 510 hosts. The R1 LAN has a subnet number of 10.4.0.0, a range of valid addresses of 10.4.0.1 through 10.5.255.254, with a subnet broadcast address of 10.5.255.255. Note that odd-looking addresses 10.4.4.255 and 10.5.0.0 are inside the range of valid IP addresses.

This explanation makes no sense. Either the mask needs to change to /15 with 2^17-2 valid hosts OR change 10.5.0.0 /23 to 10.4.5.0 /23.

Please try obtaining the errata for book so I can see how they fixed this one. I'd expect the later (10.4.5.0 /23).

Thanks,

Georgemc

Daniel333

This is fromt hr Cisco CCNA Question Engine, it was just a copy paste from the engine. I have patched and downloaded updates but seems most of these books are just packed with errors.

This was is at least a type I figure...