BGP guides

Short guides to public routing data, written for people who look at BGP routes as part of their job and for anyone learning to read them. Each one uses real maps from this site.

• How to read a BGP mapWhat the boxes, arrows, numbers and colours on a map mean.
• How to find the upstream providers of a networkReading transit providers from AS paths, and what the shares mean.
• Which network announces an IP address?From an address to its prefix and origin AS, and when whois disagrees.
• What is an AS path?How the AS path is written and used, and what prepending does.
• Tier 1 networksThe transit-free networks, with a link to each one's map.