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IP subnet

I knw this is quite simpe, trickish too, what is the best way to summarise

192.2.1.0

192.2.3.0

192.2.5.0

3 REPLIES

Re: IP subnet

Hi,

You can summarize as follows:

192.2.0.0/21

However, the above includes other subnets as 192.2.0.x, 192.2.6.x, 192.2.7.x

So, if you see overlapping problems, better not summarize.

If the above won't cause problems, go for it.

Federico.

Re: IP subnet

Hi

192.2.0.0/21

Regards

Chetan Kumar

Hall of Fame Super Silver

Re: IP subnet

Hello Just,

you need to look at the third byte write it in binary

1 = 0000 0|001

3 = 0000 0|011

5 = 0000 0|101

you need to look at the common bits from the LEFT, that are the first 5 bits before '|' this means the inclusive aggregate (that includes also other subnets) is:

moving three bits to the left from /24 boundary  : 24-3 = 21 this is the prefix length

192.2.0.0/21

if you look at summary routes that do not include other subnets the answer is negative: there is no way to aggregate these subnets without including other ones because they are not contigous

the fact that all of them have the last bit set to 1 in common is not useful

Hope to help

Giuseppe

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