BGP has a lot of moving parts. The state machine. The 13-step path-selection algorithm. The dozen knobs that influence which path wins. The exact words to type when adjacency is stuck in OpenSent. The PingLabz BGP Field Reference puts all of it on nine printable pages so you can stop scrolling docs at 2am.
(This article is part of the PingLabz BGP series - the full BGP guide maps the whole cluster in reading order.)
What's inside
- Page 1 - Quick Reference. Protocol facts, message types, the seven major path attributes compared side by side, and the AS-path regex patterns you actually use.
- Page 2 - Neighbor State Machine. The full BGP FSM as a diagram (Idle to Established), state interpretation, the TCP/179 test, and the adjacency-requirements checklist.
- Page 3 - Configuration Patterns. Basic eBGP, iBGP with loopbacks plus next-hop-self, eBGP-multihop, address-family style, authentication, maximum-prefix, TTL security.
- Page 4 - Path Attributes and Best-Path Selection. The 13-step Cisco best-path order with gotchas, plus a "which lever to use" decision table for influencing path selection.
- Page 5 - Troubleshooting Decision Tree. Six symptom branches (Idle/Active, OpenSent/OpenConfirm fail, Established but no prefixes, BGP table but not RIB, network statement not advertising, route flapping), each with likely causes and the show command to confirm.
- Page 6 - Verification and Debug Commands. All the show commands you actually use, grouped by purpose, plus soft-refresh and debug commands with production-care warnings.
- Page 7 - Reading the show Output (Annotated). Real captures from a 3-router lab built in Cisco Modeling Labs (eBGP plus iBGP, both visible from one router), with field-by-field explanations of what each column means.
- Page 8 - Copy-Paste Templates. Eight working IOS XE templates: eBGP edge, iBGP with next-hop-self, route reflector, prefix-list filter, route-map LP, AS-path prepending, aggregate, default-originate.
- Page 9 - Best Practices and Change Checklists. Eighteen practices that have saved engineers from 3am pages, plus pre-change capture commands and post-change verification.
It is print-friendly, single-column where it needs to be, dense where it can be. Engineers print these and tape them to their monitor. That is the goal.
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