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Summarization doubt

I have trying to make this exercice about Summarization,

 

Duda.png

 

 

 

After my calculations I tought the correct answer maybe B, D and E, the simulator says the correct is B and E, why they are the answer and not E and D for example?

 

Thanks!

 

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1 ACCEPTED SOLUTION

Accepted Solutions
Advocate

Re: Summarization doubt

Hi @RennyGalindez ,

 

After summarizing the networks, the result was:

 192.168.176.0/21 = 192.168.1011 0|000.0

This indicates that the networks connected to R2 must be equal until the cut of the mask (/21)

 

Options A and C do not meet this condition, so they are not one of the networks connected to R2.

 

Option B meets the condition:

192.168.183.41 = 192.168.1011 0111.0010 1001

 

Option E meets the condition:

192.168.179.4 = 192.168.1011 0011.0000 0100

 

Option D meets the condition, but it is a broadcast address, so it will not be a viable destination ip (only unicast addresses are routed from one router to another):

192.168.183.255 = 192.168.1011 0111.1111 1111

 

Regards

3 REPLIES 3
Advocate

Re: Summarization doubt

Hi @RennyGalindez ,

 

After summarizing the networks, the result was:

 192.168.176.0/21 = 192.168.1011 0|000.0

This indicates that the networks connected to R2 must be equal until the cut of the mask (/21)

 

Options A and C do not meet this condition, so they are not one of the networks connected to R2.

 

Option B meets the condition:

192.168.183.41 = 192.168.1011 0111.0010 1001

 

Option E meets the condition:

192.168.179.4 = 192.168.1011 0011.0000 0100

 

Option D meets the condition, but it is a broadcast address, so it will not be a viable destination ip (only unicast addresses are routed from one router to another):

192.168.183.255 = 192.168.1011 0111.1111 1111

 

Regards

Cisco Employee

Re: Summarization doubt

Hi Luis,

 

> Option D meets the condition, but it is a broadcast address, so it will not be a viable destination ip (only unicast addresses are > routed from one router to another):

 

This subnet is not directly connected, therefore this would not prevent traffic to this destination from being forwarded from R1 to R2.

 

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Cisco Employee

Re: Summarization doubt

You are correct. D is also correct. R1 would forward packets with destination address 192.168.183.255 to R2.

 

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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