Hello Shivam
Yes, you can summarize using classless masks. That’s part of what CIDR is (Classless Inter Domain Routing). For example, you can summarize the following networks
10.1.16.0/23
10.1.18.0/23
10.1.20.0/23
using the following summarization: 10.1.16.0/21
None of the subnet masks are classsful in this scenario.
If you can create a single summarized route to include all of your routes, then you can go ahead and do it. However, you must ensure that within the summary, there are no additional networks that may require a different routing path.
In my example above, 10.1.16.0/21 also includes 10.1.22.0/23, which was not one of the three networks being summarized. If that network actually exists somewhere else, and is routable via a different path, then you can’t use this summarization. What you can do is summarize the first two networks using 10.1.16.0/22 and keep 10.1.20.0/23 as it is.
I hope this has been helpful!
Laz