iBGP Lab: Route Reflector & Next-Hop Self

Overview

This lab demonstrates key iBGP concepts:

• iBGP split-horizon
• Route Reflector (RR)
• Next-Hop Self

Goal: Understand how iBGP behaves in non-full-mesh topologies and how RR + next-hop-self solve route propagation issues. OSPF is used between the iBGP peers for reachability.

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Topology

Devices:

• R1 → Route Reflector (AS 65000)
• R2, R3 → iBGP Clients
• R4 → eBGP Peer (AS 65001)

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IP Addressing

Device	Loopback	Links
R1	1.1.1.1/32	R1-R2: 10.0.12.1/30, R1-R3: 10.0.13.1/30, R1-R4: 10.0.24.1/30
R2	2.2.2.2/32	R1-R2: 10.0.12.2/30
R3	3.3.3.3/32	R1-R3: 10.0.13.2/30
R4	4.4.4.4/32	R1-R4: 10.0.24.2/30

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Before RR & Next-Hop Self

• R1 sees the 2.2.2.2 and 3.3.3.3 networks from its iBGP peers but does not advertise them due to the iBGP split-horizon rule.
• R1 sees 4.4.4.4 from its eBGP peer and advertises it to iBGP peers without rewriting the next-hop, which is a problem because there is no route to R4 in the routing table of R2 and R3.

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After RR & Next-Hop Self

• R1 is configured as a Route Reflector for its iBGP peers → R2 sees 3.3.3.3 and R3 sees 2.2.2.2.
• R1 is configured with Next-Hop Self → R2/R3 now see 4.4.4.4 with next-hop R1, and the route is installed in the routing table.

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