Here's how best path selection works in practice.
Your router learns from sources:
- Path A: LOCAL_PREF , AS_PATH [, ]
- Path B: LOCAL_PREF , AS_PATH [, , ]
- Path C: LOCAL_PREF , AS_PATH [, ]
Step : LOCAL_PREF. Path B has the highest (). Path B wins.
If Path B had LOCAL_PREF like the others:
Step : AS_PATH length. Path A and C have length . Path B has length . Path B is eliminated. Tie between A and C.
Continue tiebreaking with ORIGIN, MED, eBGP/iBGP preference, IGP cost, then finally router ID.