network-bgp-diagnostics

Topics in the source

• Network BGP Diagnostics
• When to Use
• Read-Only Triage Flow
• State Interpretation
• Transport Checks
• Route Policy Checks
• AS Path And Prefix Review
• Parser Pattern

Use this skill when a BGP session is down, flapping, established with missing routes, or advertising unexpected prefixes. The default workflow is read-only evidence collection; policy and reset actions belong in a reviewed change window. BGP neighbors are stuck in Idle, Connect, Active, OpenSent, or OpenConfirm. A session is Established but expected prefixes are missing. A route-map, prefix-list, max-prefix limit, or AS path policy may be filtering routes. You need before/after evidence for a BGP change. You are reviewing automation that parses BGP summary output. 1. Identify the exact neighbor, address family, VRF, and local/remote ASNs. 2. Capture summary state and last reset reason. 3. Prove reachability to the peer source address. 4. Check route policy references before assuming transport failure. 5. Compare advertised, received, and installed routes where the platform supports those commands. Use platform-specific address-family commands when the device uses VRFs, IPv6, VPNv4, or EVPN. Do not assume global IPv4 unicast. | State | First checks | | --- | --- | | Established with prefix count | Route exchange is up; inspect policy and table selection | | Established with zero pre

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