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Loopbacks are /32 host addresses that stay up regardless of physical interface state, so they are used as router IDs, BGP peering sources, management targets and MPLS LSP endpoints. Reserving one contiguous block — commonly out of 10.255.0.0/16 — lets every loopback be covered by one summary route and one management ACL.
Loopback block
addresses = devices x loopbacks per device; covering prefix = 32 - ceil(log2(addresses)); each loopback is configured as /32
A /32 wastes nothing and cannot be affected by link failure, so protocols that source packets from it stay stable even when physical interfaces flap.
Yes. A dedicated range keeps summarisation tight and makes management-plane filters, SNMP allow-lists and TACACS rules simple to write.