Unit 14: BGP Unnumbered

Per-unit concept, checklist, and command drill page

Unit 14 of 14

Objective

Run BGP peering over IPv6 link-local transport while advertising IPv4 routes at scale.

Concept Notes

BGP unnumbered replaces per-link IPv4 addressing overhead with IPv6 link-local transport while preserving IPv4 route exchange. The operational value is reduced config surface and faster large-fabric scaling.

Troubleshooting unnumbered fabrics requires comfort with mixed control-plane and forwarding semantics. Validate session health, next-hop interpretation, and route installation in that order.

Coverage Checklist

BGP unnumbered model and IPv6 link-local peering behavior.
RFC 5549 and RFC 8950 extended next-hop encoding fundamentals.
Reduction of per-link IPv4 management overhead.
Operational verification and traceroute interpretation quirks.
Troubleshooting expectations for unnumbered sessions.

Practice Outcomes

Explain why unnumbered design improves scale and reduces config burden.
Verify sessions and route installation even when hop display looks different.
Use loopback and management addressing consistently with unnumbered links.

Command Drills

vtysh -c 'show bgp summary'

Validate unnumbered peering health.

vtysh -c 'show ip route bgp'

Confirm IPv4 route installation with IPv6 next-hop transport.

ip -6 addr show

Inspect link-local addressing used by unnumbered peer sessions.

Navigation

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