300-320 · Question #76
Which two ways to manage scalability issues inside an IBGP domain with 20 or more routers are recommended? (Choose two.)
The correct answer is A. Configure route reflectors. D. Configure confederations. IBGP requires a full mesh of sessions by default - every IBGP speaker must peer with every other, which grows as n*(n-1)/2. With 20+ routers this becomes unmanageable. The two standard solutions are: Route reflectors (A) - a designated router (RR) reflects IBGP routes to its…
Question
Which two ways to manage scalability issues inside an IBGP domain with 20 or more routers are recommended? (Choose two.)
Options
- AConfigure route reflectors.
- BUse OSPF instead of EIGRP as an underlying routing protocol.
- CCreate a full mesh at Layer 1.
- DConfigure confederations.
- EConfigure static routes between all routers.
How the community answered
(43 responses)- A91% (39)
- B5% (2)
- C2% (1)
- E2% (1)
Explanation
IBGP requires a full mesh of sessions by default - every IBGP speaker must peer with every other, which grows as n*(n-1)/2. With 20+ routers this becomes unmanageable. The two standard solutions are: Route reflectors (A) - a designated router (RR) reflects IBGP routes to its clients, eliminating the full mesh requirement; and Confederations (D) - the AS is divided into sub-ASes that use EBGP-like peering between them, dramatically reducing full-mesh session counts within each sub-AS. Using OSPF vs. EIGRP (B) is irrelevant to IBGP mesh scaling, a full Layer 1 mesh (C) is impractical, and static routes (E) defeat the purpose of BGP.
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