BGP Tools

Route Filter Generator

Paste IPv4 or IPv6 prefixes and generate reusable route-filter snippets for several common network OS formats.

Inline qualifiers such as “10.0.0.0/8 le 24” are supported.

The goal is to turn a reviewed list of prefixes into a clean starting configuration quickly, without rewriting the same logic every time you move between Cisco, Junos, Bird, or FRRouting syntax.

Typical Workflow

This page works well when onboarding a customer, tightening an import policy, or translating an internal prefix list into a vendor-specific syntax for review. You can paste plain prefixes or prefixes with qualifiers, choose the target platform, then generate a block that is close to production-ready before doing your normal peer review and device-specific validation.

How To Review The Output

The generated config should be treated as a draft that saves typing, not as something to paste blindly into a live network. Check that the platform, action verb, and list name match your environment. For qualified entries, pay attention to le and ge semantics because a small mistake there can widen acceptance far more than intended.

Where Operators Usually Trip

The common failure modes are mixing IPv4 and IPv6 policy assumptions, carrying over the wrong action from a previous use, or generating a filter from prefix data that was never cleaned in the first place. If you are receiving IRR or customer-supplied data, validate the input before generating anything. This tool helps with syntax and consistency; it does not prove that the underlying routing policy is correct.