---
type: SNMP Concept
title: "AgentX: SNMP Master Agent vs Subagent Explained"
description: "AgentX RFC 2741: master agent owns UDP 161, subagents register OID subtrees; SMUX deprecated."
resource: "https://snmp-monitoring.info/what-is-snmp/architecture/agentx/"
tags: [what-is-snmp]
timestamp: 2026-07-10T00:00:00Z
---

# AgentX: SNMP Master Agent vs Subagent Explained

AgentX RFC 2741: master agent owns UDP 161, subagents register OID subtrees; SMUX deprecated.

## Related concepts

- Up: [SNMP Architecture: Manager, Agent, MIB & Managed Device](/what-is-snmp/architecture/index.md)

## Frequently asked questions

### What is AgentX in SNMP?

AgentX is the Agent Extensibility Protocol (RFC 2741) that lets a master agent delegate MIB subtrees to subagents while still presenting one SNMP agent on UDP 161.

### Difference between master agent and subagent?

The master owns the SNMP port and registration table and talks to managers. Subagents register OID ranges and serve those objects over AgentX to the master.

### Is SMUX still used?

SMUX (RFC 1227) is the older extensibility mechanism and is deprecated in favor of AgentX. Don't start new designs on SMUX.

### How do I enable AgentX in net-snmp?

Configure the master with master agentx (and related socket settings) in snmpd.conf, restart snmpd, then run subagents that connect and register. Details: snmpd.conf.

## Source

Concept generated from https://snmp-monitoring.info/what-is-snmp/architecture/agentx/ — the SNMP Monitoring vendor-neutral knowledge base. Content is limited to what that page states (no external claims added here).