What does this simulator show?

It shows the winning route for each prefix at a selected target ASN, including the AS path and a graph of how the chosen route propagated.

Help

BGP Simulator FAQ

Q: How are routes selected?

The simulator prefers customer routes over peer routes over provider routes. Ties then go to shorter AS paths, then lower next-hop ASNs.

A readable reference for the questions people ask first: what BGP is, what this BGP simulator is actually doing, how the BGP simulation works, and how to interpret what you see on screen.

Mental Model

Origin AS → Transit AS → Target AS

BGP is about which network path gets installed, not just who is geographically closest.

The simulator focuses on the winning path at one target ASN, then explains why that route won.

What Is BGP?

BGP, or Border Gateway Protocol, is the routing protocol networks use to announce which IP prefixes they can reach across the internet. Each Autonomous System advertises routes to neighbors, receives competing routes back, and picks one best route per destination prefix.

That means the internet is held together by route announcements between independent networks, not by one global controller. BGP is the protocol that lets those networks exchange reachability information while still applying their own policy.

What Does The Simulator Show?

The simulator shows the winning route for each prefix at a selected target ASN. For every visible result, it can display the chosen AS path, the inferred business relationship on each hop, and a route graph that follows the selected path from origin to target.

The important limitation is that this is not trying to render the full internet at once. It is focused on making one target ASN’s decision understandable.

How Are Routes Selected?

The simulator follows the assignment’s BGP ranking model: relationship preference first, then AS-path length, then next-hop ASN as a tie-breaker.

1. Relationship Customer routes beat peer routes, and peer routes beat provider routes.

2. Path Length If relationship is tied, the shorter AS path wins.

3. Tie Break If both still tie, the lower next-hop ASN wins.

What Is ROV?

ROV stands for Route Origin Validation. In the simulator, if an ASN deploys ROV, it rejects announcements that are marked invalid instead of storing them as candidates. That makes it possible to compare how a route spreads when some networks enforce origin validation and others do not.

Do I Need To Install Anything?

No. The live site runs entirely in the browser using WebAssembly. You do not need to install a backend service, a CLI tool, or any additional dependencies just to use the simulator.

Can I Upload My Own Data?

Yes. Use the custom upload flow to provide your own graph file, announcements CSV, and optional ROV ASN file. If you leave one input blank, the simulator can fall back to the bundled default for that specific input.

If you need the exact accepted formats, use the File Formats page. If you want the background concepts and simulator mechanics in one place, use the BGP Guide.