IS-IS Config Builder

Build Cisco IOS IS-IS configurations with an interactive NET address helper (area + system-id + NSEL), level controls, wide metrics, authentication, and common SP options. Bonus tip sheet at the top explains the IS-IS PDU structure in plain English.

NET Address Builder

IS-IS uses an OSI NET address: AFI.Area.System-ID.NSEL. The router ID (system-id) is often derived from a loopback. NSEL is always 00 for IS-IS.

AFI (fixed)

Area ID

System-ID (from loopback 10.255.0.1)

NSEL

Generated NET: 49.0001.1025.5000.0001.00

Tip: to derive a system-id from IPv4 loopback 10.255.0.1, pad to 12 digits 010255000001 → group as 0102.5500.0001. This builder auto-formats as you type.