Firewall CIDR List Optimizer
Consolidate equivalent address sets.
Firewall CIDR List Optimizer: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
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How Firewall CIDR List Optimizer Works?
The Firewall CIDR List Optimizer works by removing duplicate entries, removing entries contained in other entries, and joining adjacent entries into larger CIDR blocks, while keeping exactly the same address coverage.
Paste the address list
Enter the firewall object or rule source list.
Remove duplicates
Identical entries collapse to 1.
Remove contained entries
Entries inside a broader entry add nothing and are dropped.
Join adjacent blocks
Aligned neighbors merge into shorter prefixes. The tool reports the entry count before and after.
Firewall CIDR List Optimizer Formula
The Firewall CIDR List Optimizer formula is Optimized = CIDR(merge(unique(Input))), with identical address coverage before and after.
Duplicate removal
unique(list)Exact repeats.
Containment removal
drop B when A ⊇ BNested entries.
Adjacency merge
2 × /n aligned → 1 × /(n−1)Neighbor blocks.
Reduction
(before − after) ÷ before × 100 %Entry savings.
Worked example: 9 entries
Input : 10.1.0.0/24, 10.1.1.0/24, 10.1.0.0/24, 10.1.0.128/25,
10.1.2.0/23, 192.168.5.0/25, 192.168.5.128/25, 172.16.0.10/32, 172.16.0.0/24
Output: 10.1.0.0/22, 172.16.0.0/24, 192.168.5.0/24
Entries: 9 → 3Firewall CIDR List Optimizer Conversion Table
The Firewall CIDR List Optimizer conversion table shows the action taken on each of the 9 input entries in the worked example.
| Input Entry | Action | Final Entry |
|---|---|---|
| 10.1.0.0/24 | Merged | 10.1.0.0/22 |
| 10.1.1.0/24 | Merged | 10.1.0.0/22 |
| 10.1.0.0/24 (repeat) | Removed: duplicate | 10.1.0.0/22 |
| 10.1.0.128/25 | Removed: contained in 10.1.0.0/24 | 10.1.0.0/22 |
| 10.1.2.0/23 | Merged | 10.1.0.0/22 |
| 192.168.5.0/25 | Merged | 192.168.5.0/24 |
| 192.168.5.128/25 | Merged | 192.168.5.0/24 |
| 172.16.0.10/32 | Removed: contained in 172.16.0.0/24 | 172.16.0.0/24 |
| 172.16.0.0/24 | Kept | 172.16.0.0/24 |
What is Firewall CIDR List Optimizer?
The Firewall CIDR List Optimizer is a tool that shrinks a firewall address list to the fewest CIDR entries with exactly the same coverage.
Firewall object groups grow by copy and paste. Over time they collect repeats, entries nested inside other entries, and neighbors that should be 1 block. Long lists slow rule reviews, consume rule memory on hardware platforms, and hit hard limits in cloud security groups.
The optimizer never widens access. Every address allowed before is allowed after, and no new address is added.
What are the uses of Firewall CIDR List Optimizer?
There are 4 main uses of the Firewall CIDR List Optimizer, including rule cleanup, cloud limit compliance, and audits.
Cleaning up firewall rules
Object groups with hundreds of entries shrink before a firewall migration.
Staying within cloud limits
AWS security groups allow 60 inbound rules by default. Optimized lists fit within the quota.
Speeding up audits
Shorter lists are faster to review line by line.
Reducing TCAM usage
Hardware firewalls and switches store fewer entries in ternary content-addressable memory.