The Internet Has No GPS: How BGP Policy Steers Your Packets
BGP does not pick the shortest path. Local preference, communities, and peering contracts steer traffic. Learn to read policy with live lookup and looking glass tools.
THE BGPLOOKUP JOURNAL
Category: <span>BGP & Routing</span>
Using a BGP Looking Glass When Traffic Takes a Wrong Turn
How to use a multi-collector BGP looking glass to compare AS paths and next hops worldwide when a site is slow or unreachable from only some regions.
What BGP Actually Does (and Why Your Packets Depend on It)
A plain-English guide to Border Gateway Protocol: autonomous systems, prefixes, AS paths, and how live BGP lookup tools reveal who announces your traffic.
BGP communities are not decoration
A community is a note you staple to a route. If nobody agreed what the note means, you just invented folklore.
Traceroute is not a looking glass
Traceroute is a story packets tell. A looking glass is the table. I will not let the story fire the table.
BGP route leak vs hijack: how to tell them apart
A leak and a hijack can look the same in one collector. The origin, the path, and who is embarrassed usually do not.
When the origin ASN changes overnight
A new origin ASN is either a migration, a merger, a leak, or a hijack. Here is the checklist I run before I decide which kind of morning it is.
Reading an AS path without lying to yourself
An AS path is a rumor with good manners. Here is how I read one when the looking glass, the customer, and the traceroute all disagree.
How a BGP hijack actually looks from a looking glass
A BGP hijack rarely announces itself with a siren. It looks like a shorter path, a new origin ASN, and a Tuesday that suddenly got quiet.