The protocol variable has includeAll enabled, so Grafana auto-quotes
its value ('IS-IS_L2'); the SQL then wrapped it again, producing
''IS-IS_L2'' and a syntax error that blanked the node graph. Replace
the quoted equality filter with IN ($protocol) — Grafana already
emits a quoted CSV — and make the variable multi-select so "All"
expands cleanly.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>