OSPF ABR vs ASBR
ABR connects OSPF areas; ASBR injects routes from outside OSPF into OSPF.
Updated: 2026-03-05
Definition
An ABR (Area Border Router) connects different OSPF areas and maintains separate LSDBs per area.
An ASBR (Autonomous System Boundary Router) redistributes routes from other routing sources into OSPF.
Key points
- ABR = between areas
- ASBR = redistribution boundary
- Both affect route propagation and summarization
Common mistakes
- Confusing ABR and ASBR roles in design questions.
- Redistributing too broadly and creating instability.
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