Route Summarization
Paste IPv4 prefixes. Adjacent pairs that form a valid shorter prefix are merged, and a prefix already inside another is dropped. The routes that remain cover the same addresses you entered.
Which pairs can merge
Two prefixes merge when they have the same length, sit next to each other, and the lower one starts on the boundary of the shorter prefix. 10.0.0.0/24 and 10.0.1.0/24 become 10.0.0.0/23. 10.0.2.0/24 has nothing beside it to pair with, so it stays.
192.168.1.0/25 and 192.168.1.128/25 are that kind of pair, and they become exactly 192.168.1.0/24. A /24 typed inside a /16 disappears, because the /16 already covers it.
Paste the summary routes when a gap must stay out of the aggregate. 10.0.0.0/23 and 10.0.2.0/24 together contain only the three /24s in the example. A peer that receives 10.0.0.0/22 instead will also send traffic for 10.0.3.0/24.
Questions
The merger returns one subnet, even when that subnet contains addresses you did not list. Summarization returns every route needed to cover the same addresses and no others. A gap stays a separate route.
They are not adjacent. The single prefix that contains both is 10.0.0.0/22, and that prefix also contains 10.0.1.0/24 and 10.0.3.0/24. Those extra addresses are not added here.
Yes. 192.168.0.0/26, 192.168.0.64/26, 192.168.0.128/26, and 192.168.0.192/26 are exactly 192.168.0.0/24. Pairs merge until no aligned pair is left.
Only equal lengths merge, and only when the lower one starts on the parent boundary. A /24 beside a /23 is not a pair. If the missing sibling /24 is also in the list, those two /24s become a /23, and that new /23 can then merge with its neighbor.
Sources
Reviewed 8 October 2026. The methodology page records what these labels do not cover.
