A BGP routing table contains multiple routes to the same destination prefix.

The Aruba AOS-CX BGP Best Path Selection Process determines which route becomes the active (>) route in the BGP routing table.

This process is consistent with RFC 4271 but detailed in HPE’s Aruba AOS-CX Routing Guide and ACSP Study Guide – BGP and Dynamic Routing.

Extract 1 — BGP Path Selection Hierarchy (Aruba AOS-CX Routing Guide)

“When multiple BGP routes exist to the same destination, the router uses the following decision sequence to select the best path:

Highest LOCAL_PREFERENCE

Lowest AS_PATH length

Lowest ORIGIN type (IGP ‘i’ preferred over EGP ‘e’, preferred over Incomplete ‘?’)

Lowest MULTI_EXIT_DISC (MED) if received from the same AS

Lowest IGP cost to the next hop (closest exit)

Lowest BGP router ID as tie-breaker.”

Extract 2 — Aruba Certified Switching Professional (ACSP) Study Guide – BGP Path Decision

“Local Preference is the first and most significant criterion within a single AS.

A higher Local Preference value indicates a preferred exit.

If multiple routes have equal Local Preference, the router compares their Origin Codes.

An Origin Code of ‘i’ (IGP) is preferred over ‘?’ (Incomplete).

If still tied, the route with the lowest IGP cost to the next-hop is chosen as best.”

Step-by-Step Application to the Table

Step 1 – Local Preference

Routes B, D, and E have Local Preference = 100

Routes A and C have Local Preference = 0

✅ Routes A and C are eliminated.

Remaining candidates: B, D, E

Step 2 – Origin Code

D and E: Origin Code = i (IGP) → Preferred

B: Origin Code = ? (Incomplete) → Less preferred

✅ Eliminate B

Remaining candidates: D, E

Step 3 – MED / Metric

Both D and E have Metric = 0 → Still tied

Step 4 – IGP Cost / Administrative Distance

D: Distance = 200

E: Distance = 20

According to ArubaOS-CX:

“When all BGP attributes are equal, the route with the lowest internal cost (shortest IGP distance) to the next-hop is selected.”

✅ E wins because it has a lower distance (20 < 200)

Extract 3 — ArubaOS-CX Routing Reference

“The route that wins the selection process is marked with a ‘>’ symbol in the routing table.

This route is installed in the forwarding table and used for traffic forwarding.”

Final Explanation

Route E has:

Highest Local Preference (100)

Best Origin (IGP ‘i’)

Lowest IGP distance (20)

Hence, Route E is selected as the best path, and the “>” symbol is placed beside it in the BGP routing table.

✅ Final Verified Answer: E

???? Official Aruba Documentation References:

Aruba AOS-CX Routing Guide – Section: BGP Best Path Selection Criteria

Aruba Certified Switching Professional (ACSP) Study Guide – Module: BGP and Path Selection Logic

Aruba AOS-CX Configuration and Management Guide – Command: show ip bgp summary / route selection