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Webcast-Catalyst9k
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Host IP Address Summarization

Hi,

I have a few hosts on the access-list that are going to the same destination. I know I could summarize them by network, but for security reason I can only permit these specific hosts for access.

Ex: host ip 1.1.1.162 - 1.1.1.165 going to 10.10.10.10

Does anybody know how to summarize it to one line of access-list?

Thanks.

1 REPLY

Re: Host IP Address Summarization

In this case, it cannot be done in one line. Remember that you are working with binary numbers.

162 in binary equals 10100010.

It is therefore possible to summarize 162 and 163 in one line as follows: permit ip 1.1.1.162 0.0.0.1

In the same manner you can summarize 164 - 165:

permit ip 1.1.1.164 0.0.0.1.

Your minimum access-list will then consist of two lines instead of four.

If your hosts had been in the range 160-163 a oneliner would have been possible:

permit ip 1.1.1.160 0.0.0.3

This illustrates pretty well the need to choose ip adresses in such a fashion that the binary nature of these numbers is regarded.

Regards,

Leo

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