Using Cisco Prefix Lists Inside Route Maps for BGP Filtering
Prefix lists define which BGP routes match a policy. Route maps use those matches to permit routes, deny them, or change attributes such as local preference.
bgp
The Third App from J2sw: Prefix Advertisement Checker
A prefix can appear in the global BGP table and still have a routing problem. The route may originate from the wrong ASN. Its ROA may also authorize a shorter prefix but reject the advertised prefix length. Checking each part normally means pulling data from several routing tools. The J2SW Prefix Advertisement Checker, my 3rd … Read more
Introducing the J2SW BGP Community Builder
The J2SW BGP Community Builder selects documented provider communities and generates scoped policy fragments for MikroTik, Cisco, Junos, and FRRouting.
Why Your Traffic Didn’t go the way you expected
3 Mintue read timeJustin Wilson PacketsDownRange A common problem I run into when diagnosing route issues is traffic not going across the path it’s supposed to. An established BGP session only means the routers successfully exchanged routes. It says nothing about which route your router actually installed in the forwarding table. Let’s get into some … Read more
Understanding BGP Route Types: Full Routes vs Partial vs Default vs Customer Routes
5 minute read time.Justin Wilson j2sw.com When you configure a BGP session, one of the first questions is what routes you actually want to receive. If you have ever filled out a questionnaire with Hurricane Electric or another transit provider, they ask you what “kind” of routes you want. In this article, I plan to … Read more
RFC 10005: BGP Community for link capacity
RFC 10005 defines a BGP extended community that lets a router attach link bandwidth information to a route. Another router can use that value when it spreads traffic across multiple BGP paths. RFC 10005 matters because links are not always of the same capacity. This RFC provides routers with a standard way to carry bandwidth … Read more
George Washington, the Delaware, and Direct Routes
I originally posted this over on the FD-IX Bloghttps://blog.fd-ix.com/george-washington-the-delaware-and-direct-routes/ When George Washington crossed the Delaware River on Christmas night in 1776, the goal was simple. Reach the objective by the most effective path while avoiding unnecessary delays and giving the opposing force as little warning as possible. The crossing was risky, but it created a … Read more
Packets Down Range #41: New Cogent Route, The Hedge, GPC and Ritter Communications
Welcome to Packets Down Range #41.
Understanding Leaf and Spine Switching in Modern Data Centers
A leaf-and-spine design is a data center network topology that removes the traditional three-tier hierarchy and treats every path equally. Traditional three-tier networks build layers like access, distribution, and core. This structure creates choke points when traffic has to move northbound through specific devices. A leaf and spine fabric flattens that design so every leaf … Read more
Annatomy of a DDoS attack. When ports fill up
Identifying a DDoS attack requires an understanding of normal network behavior. In the left portion of the graph,
Whats in the box: Alta Labs Route10
The Alta Labs Route 10 is a clean, compact Route 10 built for people who care about throughput, simplicity, and not turning their rack into a space heater. Ten gig on tap, a tidy industrial design, and packaging that says “someone here sweats the details.”
What is an AS-SET?
An AS-SET is a collection of Autonomous System Numbers grouped under a single name. Rather than listing each ASN individually in your routing policy, you just refer to the set, and the routing registry handles the details. You can think of it like a mailing list for networks.