Which three methods can be used to reduce the full-mesh IBGP requirement in a service provider core network? (Choose three.)

The correct answer is A. Implement route reflectors C. Implement confederations D. Implement MPLS (LDP) in the core network on all the PE and P routers. The IBGP full-mesh rule (every IBGP speaker must peer with every other) can be reduced by: (A) Route Reflectors - an RR re-advertises IBGP-learned routes to its clients, eliminating the need for clients to peer with each other. (C) Confederations - the AS is split into sub-ASes;

Core Routing

Question

Options

AImplement route reflectors
BEnable multi-protocol BGP sessions between all the PE routers
CImplement confederations
DImplement MPLS (LDP) in the core network on all the PE and P routers
EEnable BGP synchronization
FDisable the IBGP split-horizon rule

How the community answered

(45 responses)

A
71% (32)
B
9% (4)
E
4% (2)
F
16% (7)

Explanation

The IBGP full-mesh rule (every IBGP speaker must peer with every other) can be reduced by: (A) Route Reflectors - an RR re-advertises IBGP-learned routes to its clients, eliminating the need for clients to peer with each other. (C) Confederations - the AS is split into sub-ASes; full mesh is only required within each sub-AS, dramatically reducing total peering sessions. (D) MPLS/LDP in the core - with MPLS, P (core) routers forward traffic based on labels and do not need to participate in BGP at all; only PE (edge) routers require IBGP peering, shrinking the scope of the full-mesh requirement. Option B (multi-protocol BGP) adds address families but does not reduce mesh. Option E (BGP synchronization) actually restricts route advertisement. Option F (disabling split-horizon) would create routing loops, not reduce mesh.

Topics

#BGP Scaling#Route Reflectors#BGP Confederations#MPLS Core

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