On the BGP Best Path Selection, when two external paths from different EBGP neighbors are received, the oldest path received can be the tie break to select the best path. Which Cisco IOS command…

The `bgp best path med missing-as-worst` command modifies how BGP handles routes that do not carry a MED attribute, making them less preferred, which is related to MED comparison and not the 'oldest path' tie-breaker.

The `bgp best path compare-routerid` command forces BGP to compare the router IDs of the advertising neighbors as a tie-breaker for external paths after attributes like AS-path and MED have been evaluated. By introducing the router ID comparison earlier or more explicitly, it overrides or ensures that the 'oldest path received' criterion, which is typically a later tie-breaker, is ignored in favor of the router ID comparison.

The `bgp best path cost-community ignore` command prevents BGP from using the cost community attribute in its best path selection, which is a specific attribute and unrelated to the 'oldest path' tie-breaker.

The `bgp best path as-path ignore` command causes BGP to disregard the AS-path length when selecting the best path, which is a much earlier criterion in the algorithm and not related to ignoring the 'oldest path' tie-breaker.