Why merge CIDR blocks?
Merging helps simplify network allowlists, firewall rules, and route tables when adjacent blocks can collapse safely.
CIDR Merger
Merge overlapping and adjacent CIDR blocks
IP & Routing
π 100% client-side β your data never leaves this pagePage mode
Input
Quick CTA
Paste one CIDR block per line first to merge aggregatable ranges immediately; overlap and boundary notes stay in Deep.
Output
Merged CIDR list will appear here
π 100% client-side β’ CIDR merge planner
Next step workflow
Page reading mode
Quick keeps the summary, direct answers, and next steps so you can validate fit and get a result faster.
About this tool
CIDR Merger helps network engineers collapse overlapping or adjacent IPv4 CIDR blocks into the smallest possible summarized set. It first converts input CIDRs to ranges, merges contiguous space, then emits minimal route prefixes. This reduces ACL clutter, routing table size, and manual subnet errors during firewall, VPC, or load balancer configuration. It is especially useful for cleaning historical allowlists and preparing deterministic policy updates. The entire calculation runs in-browser with no external dependencies, making it fast and safe for internal network data handling.
Direct Answers
Should every nearby block be merged?
No. Only blocks that align correctly and preserve the intended coverage should merge.