RS-232-MIB

All MIBs › RS-232-MIB

Organization: IETF Character MIB Working Group

Last Updated: 1994-05-26

Category: Hardware and Environment, Network Interfaces

Description: Defines managed objects for RS-232-like hardware character port interfaces, including asynchronous and synchronous serial ports.

IPNetwork Monitor uses several OIDs from this MIB in network discovery and polling the applicable devices. Start monitoring RS-232-MIB with a free 30-day trial of IPNetwork Monitor.

What Is RS-232-MIB?

RS-232-MIB is a vendor-neutral IETF standards-track MIB module defining managed objects for RS-232-like hardware character ports, covering both asynchronous and synchronous serial interfaces found on network and telecom equipment. It exposes port configuration such as baud rate, parity, and signal state, plus operational status of the physical serial connection (e.g., DTR/DCD signal states). Its monitoring value is primarily hardware status of the serial port itself: whether the port is correctly configured and whether its control signals indicate an active, connected peer device. It is commonly used alongside the RS-232-like port's associated Async/Sync port MIBs (rs232AsyncPortTable, rs232SyncPortTable conventions) that build on this base module. It is deployed on console/management ports of routers, switches, modems, and terminal servers that provide serial console or dial-up access. Engineers implementing or auditing this functionality typically reference the RS-232-MIB RFC/standard documentation for the authoritative specification.

IPNetwork Monitor allows you to monitor SNMP objects defined in RS-232-MIB. Use the built-in SNMP Monitoring Browser to explore available variables, view their current values and descriptions, and select the objects you want to monitor. You can then create SNMP monitors, configure thresholds, and receive alerts when monitored values change.

Supported Devices

vendor-neutral, standards-based MIB, not tied to a specific manufacturer
routers/switches/terminal servers with serial console or modem ports

Monitoring Examples

Because sample_objects were not extracted for this module, specific instance names cannot be cited, but per RFC 1659 conventions an administrator would poll rs232PortTable entries for signal state objects (e.g., DTR, DCD, DSR) to confirm a console cable or modem connection is active. A serial port control signal unexpectedly dropping to 'off' would indicate a disconnected cable or a failed terminal server port, useful for diagnosing lost out-of-band management access.

What Can Be Monitored

serial port configuration (baud rate, parity)
control signal states (DTR/DCD/DSR)
port connection status

Imported Objects

From IF-MIB

InterfaceIndex

From RFC1213-MIB

transmission

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

Counter32
Integer32
MODULE-IDENTITY
NOTIFICATION-TYPE
OBJECT-TYPE

How to Use in IPNetwork Monitor

Example using rs232AsyncPortParityErrs OID:

Select a device implementing RS-232-MIB as the target host to create a monitor — the SNMP service should be up and running on it. Click New Monitor, then check SNMP Custom on the Favorites tab, click Next, and confirm the host. On the next page, click Select... to open the built-in SNMP MIB Browser and type rs232AsyncPortParityErrs into the Find box to locate it in the OID tree, selecting the specific row/instance you want to monitor since this is a table column, then select it and click OK. It reports the total number of characters with a parity error, input from the port since system re-initialization and while the port state was 'up' or 'test'. On the monitor's Main parameters page you can set the target's SNMP port (default 161), credentials, polling interval, and other settings — see the SNMP Monitor help for details. On the State conditions and Alerting tabs, configure when the monitor should change state and trigger an alert; since this is a Counter32-type OID, Value bounds is the most useful condition here — trigger an alert if the counter increases between polls, since a rising count of errors, failures, or discards often points to a real underlying problem. Click Finish to create the monitor; you can adjust any parameter later.

OIDs

OID symbolic	OID numeric	Type	Access	Description
rs232	1.3.6.1.2.1.10.33			The MIB module for RS-232-like hardware devices.
rs232AsyncGroup	1.3.6.1.2.1.10.33.7.1.2			A collection of objects providing information applicable to asynchronous RS-232-like interfaces.
INT rs232AsyncPortAutobaud	1.3.6.1.2.1.10.33.3.1.5	INTEGER	read-write	A control for the port's ability to automatically sense input speed. When rs232PortAutoBaud is 'enabled', a port may autobaud to values different from the set values for speed, parity, and character size. As a result a network management system may temporarily observe values different from what was previously set.
INT rs232AsyncPortBits	1.3.6.1.2.1.10.33.3.1.2	INTEGER	read-write	The port's number of bits in a character.
rs232AsyncPortEntry	1.3.6.1.2.1.10.33.3.1		not-accessible	Status and parameter values for an asynchronous port.
C32 rs232AsyncPortFramingErrs	1.3.6.1.2.1.10.33.3.1.7	Counter32	read-only	Total number of characters with a framing error, input from the port since system re-initialization and while the port state was 'up' or 'test'.
NUM rs232AsyncPortIndex	1.3.6.1.2.1.10.33.3.1.1	InterfaceIndex	read-only	A unique value for each port. Its value is the same as rs232PortIndex for the port.
C32 rs232AsyncPortOverrunErrs	1.3.6.1.2.1.10.33.3.1.8	Counter32	read-only	Total number of characters with an overrun error, input from the port since system re-initialization and while the port state was 'up' or 'test'.
INT rs232AsyncPortParity	1.3.6.1.2.1.10.33.3.1.4	INTEGER	read-write	The port's sense of a character parity bit.
C32 rs232AsyncPortParityErrsEx	1.3.6.1.2.1.10.33.3.1.6	Counter32	read-only	Total number of characters with a parity error, input from the port since system re-initialization and while the port state was 'up' or 'test'.
INT rs232AsyncPortStopBits	1.3.6.1.2.1.10.33.3.1.3	INTEGER	read-write	The port's number of stop bits.
rs232AsyncPortTable	1.3.6.1.2.1.10.33.3		not-accessible	A list of asynchronous port entries. Entries need not exist for synchronous ports.
rs232Compliance	1.3.6.1.2.1.10.33.7.2.1			The compliance statement for SNMPv2 entities which have RS-232-like hardware interfaces.
rs232Compliances	1.3.6.1.2.1.10.33.7.2
rs232Conformance	1.3.6.1.2.1.10.33.7
rs232Group	1.3.6.1.2.1.10.33.7.1.1			A collection of objects providing information applicable to all RS-232-like interfaces.
rs232Groups	1.3.6.1.2.1.10.33.7.1
C32 rs232InSigChanges	1.3.6.1.2.1.10.33.5.1.4	Counter32	read-only	The number of times the signal has changed from 'on' to 'off' or from 'off' to 'on'.
rs232InSigEntry	1.3.6.1.2.1.10.33.5.1		not-accessible	Input control signal status for a hardware port.
INT rs232InSigName	1.3.6.1.2.1.10.33.5.1.2	INTEGER	read-only	Identification of a hardware signal, as follows: rts Request to Send cts Clear to Send dsr Data Set Ready dtr Data Terminal Ready ri Ring Indicator dcd Received Line Signal Detector sq Signal Quality Detector srs Data Signaling Rate Selector srts Secondary Request to Send scts Secondary Clear to Send sdcd Secondary Received Line Signal Detector
NUM rs232InSigPortIndex	1.3.6.1.2.1.10.33.5.1.1	InterfaceIndex	read-only	The value of rs232PortIndex for the port to which this entry belongs.
INT rs232InSigState	1.3.6.1.2.1.10.33.5.1.3	INTEGER	read-only	The current signal state.
rs232InSigTable	1.3.6.1.2.1.10.33.5		not-accessible	A list of port input control signal entries implemented and visible to the software on the port, and useful to monitor.
I32 rs232Number	1.3.6.1.2.1.10.33.1	Integer32	read-only	The number of ports (regardless of their current state) in the RS-232-like general port table.
C32 rs232OutSigChanges	1.3.6.1.2.1.10.33.6.1.4	Counter32	read-only	The number of times the signal has changed from 'on' to 'off' or from 'off' to 'on'.
rs232OutSigEntry	1.3.6.1.2.1.10.33.6.1		not-accessible	Output control signal status for a hardware port.
INT rs232OutSigName	1.3.6.1.2.1.10.33.6.1.2	INTEGER	read-only	Identification of a hardware signal, as follows: rts Request to Send cts Clear to Send dsr Data Set Ready dtr Data Terminal Ready ri Ring Indicator dcd Received Line Signal Detector sq Signal Quality Detector srs Data Signaling Rate Selector srts Secondary Request to Send scts Secondary Clear to Send sdcd Secondary Received Line Signal Detector
NUM rs232OutSigPortIndex	1.3.6.1.2.1.10.33.6.1.1	InterfaceIndex	read-only	The value of rs232PortIndex for the port to which this entry belongs.
INT rs232OutSigState	1.3.6.1.2.1.10.33.6.1.3	INTEGER	read-only	The current signal state.
rs232OutSigTable	1.3.6.1.2.1.10.33.6		not-accessible	A list of port output control signal entries implemented and visible to the software on the port, and useful to monitor.
rs232PortEntry	1.3.6.1.2.1.10.33.2.1		not-accessible	Status and parameter values for a port.
NUM rs232PortIndex	1.3.6.1.2.1.10.33.2.1.1	InterfaceIndex	read-only	The value of ifIndex for the port. By convention and if possible, hardware port numbers map directly to external connectors. The value for each port must remain constant at least from one re-initialization of the network management agent to the next.
INT rs232PortInFlowType	1.3.6.1.2.1.10.33.2.1.7	INTEGER	read-write	The port's type of input flow control. 'none' indicates no flow control at this level. 'ctsRts' and 'dsrDtr' indicate use of the indicated hardware signals.
I32 rs232PortInSigNumber	1.3.6.1.2.1.10.33.2.1.3	Integer32	read-only	The number of input signals for the port in the input signal table (rs232PortInSigTable). The table contains entries only for those signals the software can detect and that are useful to observe.
I32 rs232PortInSpeed	1.3.6.1.2.1.10.33.2.1.5	Integer32	read-write	The port's input speed in bits per second. Note that non-standard values, such as 9612, are probably not allowed on most implementations.
INT rs232PortOutFlowType	1.3.6.1.2.1.10.33.2.1.8	INTEGER	read-write	The port's type of output flow control. 'none' indicates no flow control at this level. 'ctsRts' and 'dsrDtr' indicate use of the indicated hardware signals.
I32 rs232PortOutSigNumber	1.3.6.1.2.1.10.33.2.1.4	Integer32	read-only	The number of output signals for the port in the output signal table (rs232PortOutSigTable). The table contains entries only for those signals the software can assert and that are useful to observe.
I32 rs232PortOutSpeed	1.3.6.1.2.1.10.33.2.1.6	Integer32	read-write	The port's output speed in bits per second. Note that non-standard values, such as 9612, are probably not allowed on most implementations.
rs232PortTable	1.3.6.1.2.1.10.33.2		not-accessible	A list of port entries. The number of entries is given by the value of rs232Number.
INT rs232PortType	1.3.6.1.2.1.10.33.2.1.2	INTEGER	read-only	The port's hardware type.
rs232SyncGroup	1.3.6.1.2.1.10.33.7.1.3			A collection of objects providing information applicable to synchronous RS-232-like interfaces.
C32 rs232SyncPortAbortedFrames	1.3.6.1.2.1.10.33.4.1.7	Counter32	read-only	Number of frames aborted on the port due to receiving an abort sequence since system re-initialization and while the port state was 'up' or 'test'.
INT rs232SyncPortClockSource	1.3.6.1.2.1.10.33.4.1.2	INTEGER	read-write	Source of the port's bit rate clock. 'split' means the tranmit clock is internal and the receive clock is external.
INT rs232SyncPortEncoding	1.3.6.1.2.1.10.33.4.1.9	INTEGER	read-write	The bit stream encoding technique that is in effect for this port. nrz for Non-Return to Zero encoding nrzi for Non-Return to Zero Inverted encoding.
rs232SyncPortEntry	1.3.6.1.2.1.10.33.4.1		not-accessible	Status and parameter values for a synchronous port.
C32 rs232SyncPortFrameCheckErrs	1.3.6.1.2.1.10.33.4.1.3	Counter32	read-only	Total number of frames with an invalid frame check sequence, input from the port since system re-initialization and while the port state was 'up' or 'test'.
INT rs232SyncPortIdlePattern	1.3.6.1.2.1.10.33.4.1.13	INTEGER	read-write	The bit pattern used to indicate an idle line.
NUM rs232SyncPortIndex	1.3.6.1.2.1.10.33.4.1.1	InterfaceIndex	read-only	A unique value for each port. Its value is the same as rs232PortIndex for the port.
C32 rs232SyncPortInterruptedFrames	1.3.6.1.2.1.10.33.4.1.6	Counter32	read-only	Total number of frames that failed to be received or transmitted on the port due to loss of modem signals since system re-initialization and while the port state was 'up' or 'test'.
I32 rs232SyncPortMinFlags	1.3.6.1.2.1.10.33.4.1.14	Integer32	read-write	The minimum number of flag patterns this port needs in order to recognize the end of one frame and the start of the next. Plausible values are 1 and 2.
INT rs232SyncPortMode	1.3.6.1.2.1.10.33.4.1.12	INTEGER	read-write	The mode of operation of the port with respect to the direction and simultaneity of data transfer. fdx when frames on the data link can be transmitted and received at the same time hdx when frames can either be received from the data link or transmitted onto the data link but not at the same time. simplex-receive when frames can only be received on this data link. simplex-send when frames can only be sent on this data link.
C32 rs232SyncPortReceiveOverrunErrs	1.3.6.1.2.1.10.33.4.1.5	Counter32	read-only	Total number of frames that failed to be received on the port since system re-initialization and while the port state was 'up' or 'test' because the receiver did not accept the data in time.
INT rs232SyncPortRole	1.3.6.1.2.1.10.33.4.1.8	INTEGER	read-write	The role the device is playing that is using this port. dte means the device is performing the role of data terminal equipment dce means the device is performing the role of data circuit-terminating equipment.
INT rs232SyncPortRTSControl	1.3.6.1.2.1.10.33.4.1.10	INTEGER	read-write	The method used to control the Request To Send (RTS) signal. controlled when the DTE is asserts RTS each time data needs to be transmitted and drops RTS at some point after data transmission begins. If rs232SyncPortRole is 'dte', the RTS is an output signal. The device will issue a RTS and wait for a CTS from the DCE before starting to transmit. If rs232SyncPortRole is 'dce', the RTS is an input signal. The device will issue a CTS only after having received RTS and waiting the rs232SyncPortRTSCTSDelay interval. constant when the DTE constantly asserts RTS.
I32 rs232SyncPortRTSCTSDelay	1.3.6.1.2.1.10.33.4.1.11	Integer32	read-write	The interval (in milliseconds) that the DCE must wait after it sees RTS asserted before asserting CTS. This object exists in support of older synchronous devices that cannot recognize CTS within a certain interval after it asserts RTS.
rs232SyncPortTable	1.3.6.1.2.1.10.33.4		not-accessible	A list of asynchronous port entries. Entries need not exist for synchronous ports.
C32 rs232SyncPortTransmitUnderrunErrs	1.3.6.1.2.1.10.33.4.1.4	Counter32	read-only	Total number of frames that failed to be transmitted on the port since system re-initialization and while the port state was 'up' or 'test' because data was not available to the transmitter in time.
rs232SyncSDLCGroup	1.3.6.1.2.1.10.33.7.1.4			A collection of objects providing information applicable to synchronous RS-232-like interfaces running SDLC.

RFC description

RS-232 serial port hardware management and monitoring.

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