SNMP Agent Connection Tag

Help Contents

Introduction

The SNMP Agent Connection Tag Channel Tag Icon provides a connection to an SNMP agent.

The tags associated with the SNMP Agent Connection Tag can be read:

Configuration Properties

The SNMP Agent Connection Tag supports the configuration properties of the Active Channel Tag plus these properties:

Property Type Version Description
ScanInterval TIME 1.3 The interval between each read. An interval value of zero (T#0s) disables periodic query execution. See Interval and Offset for information on how timed activities are scheduled.
ScanOffset TIME 1.3 The offset added to the Interval to get the actual read time. See Interval and Offset for information on how timed activities are scheduled.
HostName WSTRING 1.3 The host name or IP Address of the SNMP Agent.
PortNumber WSTRING 1.3 The port number of the SNMP agent. The default value is 161.
SnmpVersion USINT 1.3 The version of SNMP to use. The options are:
  • 0 = SNMP Version 1,
  • 1 = SNMP Version 2c,
  • 2 = SNMP Version 3.
For best security use SNMP Version 3.
ReadCommunity WSTRING 1.3 The community password string used when the driver reads from the SNMP Agent. The default value is 'public'. Only applies when the SNMP Version is 1 or 2c.
WriteCommunity WSTRING 3.53 The community password string used when the driver writes to the SNMP Agent. The default value is 'private'. Only applies when the SNMP Version is 1 or 2c.
V3UserName WSTRING 3.48 The user name for SNMP Version 3.
V3AuthProtocol USINT 3.48 The Version 3 authentication protocol to use with the SNMP Agent. The options are:
  • 0 = None,
  • 1 = MD5,
  • 2 = SHA1.
For best security use SHA1.
V3AuthPassword WSTRING 3.48 The password for SNMP Version 3.

SNMP Security

Use this table to understand SNMP security:

SNMP Version Security Comments
Version 1 Weak The ReadCommunity and WriteCommunity strings are sent in plain text over UDP datagrams. Vulnerable to packet sniffing, and replay attacks.
Version 2c Weak The ReadCommunity and WriteCommunity strings are sent in plain text over UDP datagrams. Vulnerable to packet sniffing, and replay attacks.
Version 3
V3AuthProtocol None
None Vulnerable to replay attacks.
Version 3
V3AuthProtocol MD5
Good Password validation does not send the password in plain text over UDP datagrams. Resists replay attacks. MD5 is now considered a weak hash algorithm, however exploiting this weakness to break the security of SNMP would be difficult.
Version 3
V3AuthProtocol SHA1
Good Password validation does not send the password in plain text over UDP datagrams. Resists replay attacks.

Dynamic Properties

The SNMP Agent Connection Tag supports the dynamic properties of the Channel Tag plus these properties:

Property Type Description
ScanTimer TimerStatus The status of the scan timer.

Tag Commands

The SNMP Agent Connection Tag supports the tag commands of the Active Channel Tag plus these tag commands:

Tag Command Version Description
Refresh 1.3 Requests an immediate read of all of the tags associated with this SNMP Agent Connection Tag.

Note: Event triggered data reads (from the Refresh Tag Command) and periodic data reads (defined by the ScanInterval property) are independent. You can use the Refresh Tag Command, or the ScanInterval property, or both to determine when the tags are read.

Relationships to Other Tag Types

The SNMP Agent Connection Tag builds on the features of these tag types:

Further Information

Interval and Offset

To learn how activities are scheduled using Interval and Offset.

I/O Analog Data Point Tag

To learn about the I/O Analog Data Point Tag that can be associated with the SNMP Client Tag.

I/O Digital Data Point Tag

To learn about the I/O Digital Data Point Tag that can be associated with the SNMP Client Tag.

I/O String Data Point Tag

To learn about the I/O String Data Point Tag that can be associated with the SNMP Client Tag.

I/O Word Data Point Tag

To learn about the I/O Word Data Point Tag that can be associated with the SNMP Client Tag.

I/O Double Word Data Point Tag

To learn about the I/O Double Word Data Point Tag that can be associated with the SNMP Client Tag.

I/O Long Word Data Point Tag

To learn about the I/O Long Word Data Point Tag that can be associated with the SNMP Client Tag.

SNMP Client Driver

For an overview of the SNMP Client Driver.

Alarm Handling

To learn about alarm management.

Glossary

For the meaning of terms used in Fernhill SCADA.