Port 199SMUX (SNMP Multiplexer)
**SMUX (SNMP Unix Multiplexer)** is a protocol running primarily on port 199 that facilitates the integration of sub-agents into the overall SNMP agent framework, enabling modular management in network devices and systems. It allows different components to provide their own management information autonomously while coordinating through a central SNMP master agent..
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 8,953
2 transports registered
payload readable on path
registered with iana
caution
rank 552 of 993 · top 56%
Technical Details
what runs on :199Overview
SMUX, short for SNMP Unix Multiplexer, was designed to extend the Simple Network Management Protocol (SNMP) framework by allowing multiple sub-agents to communicate with a master SNMP agent. This architecture enables modularity, as various network services or components can provide their own management data without relying on a monolithic agent implementation.
Protocol Details
SMUX operates over TCP and UDP on port 199. It uses an ASN.1-based encoding similar to SNMP and was primarily adopted in Unix-based systems. The sub-agents connect to the master agent via SMUX, register the MIB objects they manage, and handle requests that fall under their registered sections. This approach allows the master agent to delegate specific tasks dynamically.
Usage Scenarios
Commonly, SMUX was found in Cisco and other network vendors’ equipment as well as Unix servers requiring modular SNMP management. Although largely superseded by AgentX (RFC 2741), SMUX is still relevant in legacy systems where backward compatibility or minimal changes are preferred.
Security Information
exposure of :199risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
network services averages 3.9 across 604 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp · udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
Common Vulnerabilities
- Weak Authentication: SMUX was designed with minimal security considerations, making it susceptible to unauthorized access if not properly restricted.
- Information Disclosure: Since SMUX can expose sensitive management data, attackers gaining access might gather valuable reconnaissance data.
- Man-in-the-Middle Attacks: The lack of encryption can allow attackers to intercept or spoof management data exchanges.
Common Mitigations
- Network Segmentation: Restrict access to port 199 to trusted management networks only.
- Access Controls: Use firewalls and ACLs to limit hosts permitted to connect to the SMUX interface.
- Encryption Tunneling: Employ VPNs or other encrypted channels if remote management is necessary.
- Migration: Consider migrating to more secure and modern protocols like AgentX or SNMPv3 which provide superior security, including authentication and encryption.
Related Ports
the 8 most looked-up other ports in network services — 604 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :9080 | Groove RPC | TCPUDP | Web Services | caution | 70.8k |
| :6543 | Jetnet | UDP | Network Services | caution | 65.3k |
| :5938 | TeamViewer | TCPUDP | Remote Access | caution | 65.0k |
| :8291 | Winbox MikroTik Admin | TCP | Security | caution | 62.9k |
| :3233 | WhiskerControl Protocol | TCPUDP | Network Services | caution | 61.9k |
| :3268 | Microsoft Global Catalog (GC) | TCPUDP | Security | caution | 54.6k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :3128 | Tatsoft Default HTTP Proxy | TCP | Web Services | caution | 46.8k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted