Blog

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.

BGP communities tag routes with meaning: customer route, prefer this path, do not advertise outside our region. A complete guide to standard, extended, and large BGP communities with practical policy examples.

Route maps are the primary BGP traffic engineering tool on Cisco IOS XE. Match on AS-path, community, or MED, then set attributes to steer paths. A practical guide to matching, setting, and manipulating BGP routes.

RPKI lets prefix owners sign ROAs that say which AS is authorized to originate their prefixes. Route Origin Validation rejects invalid routes. A practical guide to RPKI and ROV on Cisco IOS XE for internet-facing networks.