Collapsing many specific routes into one supernet. Same math, two exam words: summarization inside an AS (OSPF/EIGRP/RIP), aggregation between ASes (BGP).

• The summary route points at Null0 — a local loop-prevention anchor so specific routes don’t recurse into a blackhole loop.
• Benefits: smaller tables, less update traffic, faster convergence, hidden internal detail.
• BGP extras: summary-only suppresses specifics; as-set preserves loop prevention; see the blackhole trap in the BGP note.
• OSPF placement matters: area range on the ABR (inter-area), summary-address on the ASBR (external).