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BGP does not auto-advertise connected interfaces like OSPF. Routes must be injected via network, redistribution, or aggregation. Understand NLRI, withdrawn routes, and the Adj-RIB pipeline to control what you advertise.

Cisco BGP picks the best path with a 13-step algorithm. Most real decisions resolve in steps 1 to 5, but troubleshooting unexpected path selection means knowing every step. A complete walkthrough with examples.

An unauthenticated BGP session is vulnerable to TCP-based attacks and spoofed RSTs. MD5 has been the standard for decades; TCP-AO is the modern replacement. A practical guide to BGP session authentication.

A BGP default route tells a peer to send anything it does not have a more specific path for. Different injection methods, default-originate, network, redistribute, have different behaviors and failure modes. Pick carefully.

The IPv4 BGP table has over 950,000 prefixes and growing. Route aggregation lets you advertise a summary instead of many specifics, reducing the routing table burden on your peers and the internet. Configuration and gotchas.

Weight is the first step of Cisco BGP best-path selection, Cisco-proprietary, never advertised, and local to the router. The most targeted BGP traffic engineering tool when you need one router to override AS-wide policy.