Short, practical write-ups on BGP, FRR, and Containerlab: troubleshooting, gotchas, and the steps that actually fix a broken session. Each post links to a lab you can run yourself.
You prepended your ASN to shift inbound traffic and nothing changed. AS_PATH length loses to LOCAL_PREF and prepend is only a request, not a command. Why it fails.
Your eBGP session is Established but show ip bgp summary shows (Policy) and zero prefixes. RFC 8212 filters policy-less eBGP by default, with the fix in FRR.
What the *, >, i, r, and s markers in show ip bgp mean, and how to read the Network, Next Hop, Metric, LocPrf, Weight, and Path columns in FRR.
BGP route not received and nothing looks wrong? Your own ASN is in the AS_PATH and the router calls it a loop. Confirm it in FRR and fix it with allowas-in.
The prefix shows in show ip bgp but never reaches show ip route. The causes that bite FRR users, in priority order, with the vtysh commands to confirm each.
BGP stuck in Active, Idle, or Connect and never reaching Established? Here are the usual causes and the exact FRR vtysh commands to confirm each one.
Containerlab vs GNS3 vs EVE-NG, compared honestly: footprint, supported images, GUI vs YAML, licensing, and which network lab tool fits your study.