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New Member

IP Address Summarization Question

Hello. I am trying to determine the summarized IP Address for the following range of addresses:

(Since the first two octets are the same for all of the addresses, I'll just ask about the 3rd octet). Looking at the 3rd octet for the first and last addresses (decimal 8 and 88) the bit pattern stops matching in the 8th bit position of the 3rd octet. Or in binary it looks like this:



Normally when summarizing you add all of the matching bits and adjust the subnet mask accordingly to arrive at the summarized address. Since there are no bits to add, would the summarized address be simply: 0. And is the subnet mask moved over to include this bit? To put it another way, would the address read: (

Thank you for your time and feedback. Apologies if this is not terribly clear; I'm only on the first cup of coffee!



Re: IP Address Summarization Question


This summarization covers these ranges to to to 172.16..32.0 to to to to to to to to

New Member

Re: IP Address Summarization Question

Wow, now that was a fast reply! Thank you for looking at my question. Judging by your response, I"m not summarizing correctly.

New Member

Re: IP Address Summarization Question

Be careful with your summarization. By stating you have, you are advertising an IP range of through, well out of the range you specified. Assuming you have not in use as the first subnet, you can summarize which includes through The last four subnets can be summarized on their own with which advertises through Also check that your routes to null are correct if you are summarizing networks not in use to prevent routing loops.

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