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Routing & Switching · Advanced

Segment Routing Global Block (SRGB)

The label range reserved on each router for global SR-MPLS prefix SIDs, default 16000-23999 on Cisco.

Definition

The label for a prefix SID equals the SRGB base plus the SID index. Using the same SRGB on all routers keeps labels identical network-wide, simplifying troubleshooting.

Example

segment-routing global-block 16000 23999

Exam tip

Mismatched SRGBs still work but labels differ per hop; consistent SRGB is best practice.

Related terms