international student

How to determine summary IP address, wildcard mask and range.

Let's take an example of below four IP addresses. We need to find the summary address for the range of IPs shown below and find the wildcard mask for that summary address.

11.11.128.1
11.11.129.1
11.11.130.1
11.11.131.1.

We first find the wildcard mask of the summary IP address. First two columns are identical (11.11) and we know the difference is in third column.

So we get the wildcard mask by subtracting the least number (128) from the biggest in that column (131). We get 3 and this becomes the wildcard mask for the third column.

Then you put 255 in the last column, hence the wildcard mask for the summary route is 0.0.3.255.

The full summary route becomes 11.11.128.0    0.0.3.255.


How to find the range of a summarized route.

To find the range of the summarized route given the summary route and wildcard mask, you add the 2 lines.

11.11.128.0 ========> beginning of range.

0. 0. 3. 255 =========> Add to the wildcard mask

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11.11.131.255 ======> End of range