CIDR / supernet calculator
Combine contiguous networks into one summary route to keep routing tables small.
Runs on your device · nothing is uploaded
What is route summarisation?
Summarisation (supernetting) is the reverse of VLSM: instead of splitting a block into smaller subnets, you combine several contiguous networks into one larger prefix. A router can then advertise one route instead of many, which keeps routing tables smaller and hides changes inside the summarised block.
Single summary vs exact summary
- Single summary route is the smallest one prefix that covers every network you entered. If your networks have gaps, it also covers addresses you don't own, which could attract traffic for them.
- Exact summary is the fewest prefixes that cover exactly your networks and nothing else.
Example: 192.168.0.0/24 to 192.168.3.0/24 summarise perfectly to 192.168.0.0/22, because four /24s are one /22 and they start on a /22 boundary.