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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.

AS-path prepending is the go-to tool for influencing inbound BGP traffic: artificially lengthen the AS-path so remote ASes prefer your other exit. It is blunt, global, and has real security implications. When it works, and when it does not.

MED tries to influence how traffic enters your AS by suggesting which of your entry points the neighbor should prefer. It is optional non-transitive and easy to misuse. How MED actually works, and how to set it safely.

Local preference tells every router in your AS which exit to prefer for specific destinations. It rides iBGP throughout the AS and resolves in step 2 of best path. The cleanest tool for inbound exit engineering.