Question

An SP network engineer is troubleshooting outbound path selection on an IOS XR PE router. The router receives two eBGP advertisements for prefix 203.0.113.0/24. Both paths have equal weight (0), equal local preference (100), neither is locally originated, both are non-aggregate routes, and MED is not being compared because the paths come from different neighboring autonomous systems. Path 1 has an AS_PATH of '65010 65020 65030' and Path 2 has an AS_PATH of '65040 65030'. All other attributes up to this decision point are equal. Based on the BGP best-path algorithm, which path will the router select and why?

Accepted Answer

Path 2, because its AS_PATH is shorter (fewer AS hops), which is evaluated before origin code and MED.

Answer

Path 1, because it traverses more autonomous systems and is therefore considered more stable.

Answer

Path 2, because the highest-numbered originating AS (65040) is preferred as a tiebreaker.

Answer

Path 1, because BGP prefers the path whose first AS in the AS_PATH is numerically lower.