ittechlab
asked on
summarization
http://www.9tut.com/ccna-subnetting-questions-4
Question number 2
Can some one explain how the answer is D for above question.
I did study summarization but i am not clear on this question. Please explain.
Question number 2
Can some one explain how the answer is D for above question.
I did study summarization but i am not clear on this question. Please explain.
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ASKER
Thanks. Let me go thorough your notes.
ASKER
hi Akinsd,
i understand the notes. I still have few things need to be cleared. How would I able to do the following summarization question.
http://www.9tut.com/ccna-subnetting-questions-3
question 9 , i did apply the same method but not able to understand why the answer is B and D. Please explain.
i understand the notes. I still have few things need to be cleared. How would I able to do the following summarization question.
http://www.9tut.com/ccna-subnetting-questions-3
question 9 , i did apply the same method but not able to understand why the answer is B and D. Please explain.
You would need to look at the existing networks.
Core-Marketing 172.16.3.4/30 (2 hosts: 172.16.3.5 - 172.16.3.6)
Core-Sales 172.16.3.8/30 (2 hosts: 172.16.3.9 - 172.16.3.10)
Core-Admin 172.16.3.12/30 (2 hosts: 172.16.3.13 - 172.16.3.14)
Marketing LAN: 172.16.3.32/27 (30 hosts: (172.16.3.33 - 172.16.3.62)
Sales LAN: 172.16.3.64/27 (30 hosts: (172.16.3.65 - 172.16.3.94)
Admin LAN: 172.16.3.96/27 (30 hosts: (172.16.3.97 - 172.16.3.126)
So for Network A, a mask of /25 is needed to have host field large enough to accommodate the 120 hosts on the LAN.
For the link, a /30 mask is used. Answer D works and the addresses 172.16.3.1 - 172.16.3.2 would be assigned to the router interfaces.
Answer E would have addresses which have already been assigned to Marketing LAN.
Answer F would have addresses which have already been assigned to Admin LAN.
Core-Marketing 172.16.3.4/30 (2 hosts: 172.16.3.5 - 172.16.3.6)
Core-Sales 172.16.3.8/30 (2 hosts: 172.16.3.9 - 172.16.3.10)
Core-Admin 172.16.3.12/30 (2 hosts: 172.16.3.13 - 172.16.3.14)
Marketing LAN: 172.16.3.32/27 (30 hosts: (172.16.3.33 - 172.16.3.62)
Sales LAN: 172.16.3.64/27 (30 hosts: (172.16.3.65 - 172.16.3.94)
Admin LAN: 172.16.3.96/27 (30 hosts: (172.16.3.97 - 172.16.3.126)
So for Network A, a mask of /25 is needed to have host field large enough to accommodate the 120 hosts on the LAN.
For the link, a /30 mask is used. Answer D works and the addresses 172.16.3.1 - 172.16.3.2 would be assigned to the router interfaces.
Answer E would have addresses which have already been assigned to Marketing LAN.
Answer F would have addresses which have already been assigned to Admin LAN.
ASKER
sorry i mean to say question 9. Please look at the question 9 about summarization.
ASKER
i am not quite sure how reverse route summarization works.
I think you're overthinking that one. :-)
Look at it like you would a regular subnetting question.
What are the valid addresses for the 172.31.80.0/20 network?
172.31.80.1 - 172.31.95.254
Any addresses in that range would be your answers.
Look at it like you would a regular subnetting question.
What are the valid addresses for the 172.31.80.0/20 network?
172.31.80.1 - 172.31.95.254
Any addresses in that range would be your answers.
ASKER
question is /20 but how come they are using /22 in the answer?
this is where i am having confusion.
this is where i am having confusion.
The /20 is a summary route which contains a number of smaller networks. Just like 172.16.0.0/16 would be a summary for the 172.16.0.0/24, 172.16.1.0/24, 172.16.2.0/24, 172.16.3.0/24, etc.
Thanks for the points and feedback.
Let me know if you still need help or clarification
Let me know if you still need help or clarification
Of the four network in Phoenix, start with the lowest (10.4.0.0/24).
If the mask is moved 1 bit to the left (10.4.0.0/23), that summary route will include the 10.4.0.0/24 and the 10.4.1.0/24 networks. Or put another way, we now have a "summary field" (as opposed to a subnet field) of 1 bit. A 1-bit summary field includes two networks.
Moving the boundary one more bit (10.4.0.0/22), will create a summary route that includes the 10.4.0.0/24, 10.4.1.0/24, 10.4.2.0/24 and 10.4.3.0/24 networks. Or now we have a two-bit summary field which will allow 4 networks to be summarized.