Which two statements are correct about using BGP as the underlay routing protocol in an IP fabric? (Choose two.)

Question

Options

• AStatic routes are required for EBGP neighbors to establish.
• BEBGP underlay requires the multipath multiple-as parameter with the corresponding load-
• CRoute Reflection can be used in an IBGP underlay to increase control plane scalability.
• DUsing an IGP is required for an EBGP underlay.

• A
  7% (2)
• B
  76% (22)
• D
  17% (5)

Explanation

B is correct because in an EBGP underlay, each leaf and spine typically resides in a different AS, meaning ECMP paths will have different AS paths. BGP's default behavior rejects multipath routes with differing AS paths, so the multipath multiple-as (or equivalent as-path multipath-relax) parameter is essential to enable true load balancing across equal-cost links in the fabric.

C is correct because IBGP requires a full mesh by default - every router must peer with every other router (O(n²) sessions), which doesn't scale. Route Reflectors break this requirement by acting as a hub, allowing iBGP peers to only peer with the RR instead of each other, dramatically reducing session count in large fabrics.

A is wrong because EBGP peers are typically directly connected neighbors on the same subnet, so they are already reachable without static routes - no additional routing is needed to establish the peering session.

D is wrong because a major advantage of EBGP as an underlay (common in modern data center designs like BGP-only fabrics) is that it replaces the IGP entirely - no IGP is required.

Memory tip: "BGP Fabric needs two fixes: Multipath for Multiple-AS load balancing, and Reflectors to Reduce IBGP mesh." The two "MM/RR" pairs map directly to answers B and C.

No community discussion yet for this question.