SevOne NMS 5.4 Device Certification Guide

Tables and Indexing

The OID tables contain the list of OIDs and the type of data that the OID returns. The data types that are most useful for SevOne NMS reports are counters and gauges. A counter value increments sequentially and a gauge value can go up or down. Each table in the MIB can display the object type definition and indicate the table index.

A description of each OID follows the list of OIDs.

Manage Atomic SNMP Indicator Types

Perform the following steps on the Object Types page to manage SNMP atomic indicator types.

1. Click on an SNMP object type in the hierarchy to display its indicator types on the right.

2. Click Add Atomic Indicator Type or click next to an atomic indicator type to display the Add/Edit SNMP Indicator Type pop-up.

3. In the Indicator Name field, enter the name of the indicator type.

4. In the Description field, enter the name to display.

5. View the Indexed By OID you define for the object type. You cannot edit this field.

6. For certain 64 bit OIDs, click the OID (high bit) to display the SNMP OID Browser where you select an OID to describe the top 32 bits on the OID. See note below.

7. Click the OID to display the SNMP OID Browser where you select an OID to describe the object type expression.

8. Click the Indicator Type drop-down and select a type.

9. Click the Measured As drop-down and select a data unit.

10. Click the Display As drop-down and select a display unit.

11. Click the Max Value Expression to display the SNMP OID Browser where you select an OID that is the maximum value for the indicator type.

12. Click the Measured As drop-down and select a data unit.

13. Select the Default Allowed for New Devices check box to have the SNMP plugin poll the indicator type by default when the object type is enabled and you enable the SNMP plugin for a device.

14. Click Save.

Manage SNMP Synthetic Indicator Types

Synthetic indicator types enable you to perform math on multiple metrics collected from multiple indicators on a single monitored object in order to calculate new KPIs.

Synthetic indicator types behave similar to the Calculation Editor that enables you to create custom calculation objects that perform math on multiple metrics collected from multiple objects and/or multiple synthetic indicators that you poll via the Calculation plugin. These features enable you create your own KPIs even when those KPIs do not exist on a device such as Percentage Loss, Percent Error, and Percent Idle. Synthetic indicators are always gauge type indicators and SevOne NMS evaluates all the indicator values the synthetic indicator uses as if the value is a gauge.

1. Click on an SNMP object type in the hierarchy to display its indicator types on the right. If the object type does not have any indicator types, the Add Synthetic Indicator Type button does not appear.

2. Click Add Synthetic Indicator Type or click next to a synthetic indicator type to display the Add/Edit Synthetic Indicator Type pop-up.

3. In the Indicator Name field, enter the name of the synthetic indicator type.

4. In the Description field, enter the name to display.

5. The Synthetic Indicator Expression field enables you to define the calculation.

   If the border around the field turns red, your calculation is invalid and your graph results will be erroneous.

   1. Click an indicator type in the Available Source Indicators field and drag it to the Synthetic Indicator Expression field. The Available Source Indicators field contains the indicator types associated to the object type you select in the hierarchy.

   2. Enter applicable operators in the Synthetic Indicator Expression field to formulate the calculation. See the Acceptable Operators section below.

   3. Drag additional source indicator types and enter additional mathematical symbols to create the expression in the Synthetic Indicator Expression field.

6. The Maximum Value Expression field enables you to define the indicator type maximum value calculation.

   1. Click an indicator type in the Available Source Indicators field and drag it to the Maximum Value Expression field.

   2. Enter applicable operators in the Maximum Value Expression field to formulate the calculation. See the Acceptable Operators section below.

   3. Drag additional source indicator types and enter additional mathematical symbols to create the expression in the Maximum Value Expression field.

7. Click the Measure As drop-down and select the unit of measure to use to measure the data.

8. Click the Display As drop-down and select the unit of measure in which a display the data.

9. Select the Default Allowed for New Devices check box to have the plugin poll the indicator type by default when the object type is enabled and you enable the plugin for a device.

10. Click Save.

Acceptable Operators

Your expression formula can include the following characters:

• + add

• - subtract

• * multiply

• / device

• & & logical and

• || logical or

• <= less or equal

• >= greater or equal

• ! not equal

• == equal

• > greater than

• < less than

• ^ raise x to the power of y

• % modulus

• ?: if then else

If your calculation results in either of the following invalid values, there will be a gap in your graph: Not a Number (NAN) and Infinity (+/-INF). The following is how SevOne NMS attempts to prevent invalid values.
In sequence of processing:

• Zero divided by zero results in NAN.

• Any positive value divided by zero results in +INF.

• Any negative value divided by zero results in -INF.

• Zero multiplied by +/-INF results in NAN.

• Any value added to, subtracted from, multiplied by, divided by, or divided from NAN results in NAN.

• Any value compared to NAN (<, <=, ==, >=, >) results in 0. NAN != NAN.

• Any value compared to +INF is less than +INF, except that +INF == +INF

• Any value compared to -INF is greater than -INF, except that -INF == -INF

• Any value added to or subtracted from +INF results in +INF

• Any positive value multiplied by +/-INF results in +/-INF

• Any value divided by +/-INF results in 0

Index Types

Integer - A single number of any size.

String (with length) - A string of text, prefixed with the number of characters and followed by the ASCII value of each character.

String (no length) - A string where the length is not prefixed.

Number (with length) - A string index where the numbers do not have an ASCII meaning.

Number (no length) - A string index with no length where the numbers do not have an ASCII meaning.

Statements

A statement is the atomic unit of a script. A statement can assign a value to a variable or a statement can be an expression that evaluates to some value. Each statement evaluates to some value upon execution, (e.g., For a variable assignment, the value of the statement is the value of the variable).

Statements are lists of expressions and expression chains may be very complex and long. All S3 statements must end in a semicolon <;>. The last statement in a script may omit the semicolon.

Simple statement:

Expression ;

List statement where the final value is the concatenation of both expressions:

Expression 1 Expression 2 ;

Expressions

An expression is the atomic unit of a statement. S3 is an OID-evaluation language and a text creation language. Multiple expressions can lie next to each other and their results are concatenated together. This differs from more logical and mathematical languages.

Example: 1 + 2 3 + 4

• In C there needs to be a joining operation between the 2 and the 3 because they are considered two disjointed expressions which results in a syntax error.

• In S3 this is seen as two separate expressions next to each other: 1+ 2 and 3 + 4 and the result of the statement is 37. The white space does not matter unless enclosed in quotes.

An expressions is anything that evaluates to a value. This value need not be numeric. A piece of text evaluates to itself. An expression might be the number 7, the word Hello, or a complex mathematical formula. Expressions can be chains of symbols and operators as long as the entire expression evaluates to a single value.

• Number

7

• String:

'Hello'

• Complex Formula:

( ( 1 + 2 ) / 12 + 34 ) * 10

• Variable or OID that evaluates to a number or string:

[INDEX]
.1.3.6.1.2.1.1.1.0

• Multiple grouped expressions (enclosed within parentheses) concatenated together:

( 7 'Hello' ( ( 1 + 2 ) / 12 + 34 ) * 10 [INDEX] .1.3.6.1.2.1.1.1.0 )

Variables

Variables are evaluated as OIDs to store the value of an expression. S3 has two types of variables; scalars and vectors.

• Scalar - Anything that is a single number or some text.

• Vector - An array of things. Vectors in S3 are different from vectors in normal scripting languages. Vectors in S3 are geared toward OIDs because an individual OID is represented as .<number> and a full OID is a series of .<numbers>s one after another. S3 breaks down variables into vectors by the "." character.

Variables are a name surrounded by square brackets. Variable names consist of the following characters: a-z, A-Z, 0-9, and - .

[Variable Name]

A variable assignment is an expression. The evaluation of the assignment is the new variable value. A variable assignment uses the = operator.

[Variable name] = Expression

S3 uses the following conventions to differentiate SevOne system variables from user variables to prevent user variables from overwriting system variables. There is no rule to enforce this.

• SevOne system variables use capital letters and underscores for spaces. [MY_VARIABLE]

• User variables use lowercase letters, a capital letter in the next word, and no underscore for spaces. [myVariable]

S3 can treat and evaluate variables as OIDs. Each variable must be declared before use. There is no special declaration syntax, but a variable must have an assigned value before use in an expression. Both scalar variables and vector variables are evaluated and inserted raw into the expression. S3 does nothing special to scalar variables when scalar variables are evaluated.

When a vector variable is evaluated, each of the vector variable's components is written, separated by "."s. Elements in vector variables are zero-indexed numerically. The first element starts at 0, the second starts at 1, and so on. To access a particular element of a vector variable, surround the element index in curly braces after the variable.

[Variable Name ]{Index number }

A variable cannot be used as an index number. The index number must be an actual number.

Each element in a vector variable is usually a scalar variable. There are exceptions when an element in a vector variable is another vector variable.

Some variables should not be evaluated as an OID. Enclose the variable in back ticks to prevent the variable from being evaluated as an OID. If a variable simply contains a number, the variable is treated as a normal number if not back ticked; however, it is always safe to back tick a variable to prevent improper evaluation. Text evaluates to itself. Text is considered anything enclosed in quotes. Back ticks may be in a single quoted string and that single quote string may be in a back tick quoted string.

• Single quotes (') - Single quotes are used for raw text. The content of the text is not processed in any way, e.g., 'Anything here'

• Back Ticks (`) - Back ticks are used for variable interpolation. Any variables present in the text is evaluated, e.g., `Anything here, including variables`

Indexing

When an OID is encountered, S3 tries to evaluate it. If S3 cannot evaluate the OID, then S3 adds the value of the default index to the OID, which for SNMP discovery is [INDEX]. If S3 still cannot evaluate the OID, then the OID evaluates to the empty string. This allows for very human readable and human understandable definitions for objects and indicators. However, at the loss of stringent definitions.

If an OID already has .[INDEX] appended to it, then the OID saves S3 the step.

Grouping

Parentheses ( and ) group expressions to define the sequence in which they are to be evaluated. This is commonly used in mathematical applications.

Example:

1 + 2 * 3

(which is 7)

Is not the same as:

( 1 + 2 ) * 3

(which is 9).

Parentheses can change two expressions into one expression.

Example:

( 1 + 2 3 + 4 )

Evaluates to the single value 37, which could be used by further expressions.

Operators

Operators are symbols. Operators are anything that act on an expression. There are three types of operators:

• Unary operators act on one value only, (e.g., Not).

• Binary operators act on two values, (e.g., Addition).

• Ternary operators act on three values, (e.g., ... ? ... : ... is a ternary operator in C).

Math

The common mathematical operators are applied with the usual precedence. Mathematical operators have full floating point support.

Multiplication (Standard multiplication)

Left expression * Right expression

Division (Standard division)

Left expression / Right expression

Addition (Standard addition)

Left expression + Right expression

Subtraction (Standard subtraction)

Left expression - Right expression

Comparison

Comparison operators compare two expressions that return 1 if the comparison is true or return 0 if the comparison is false.

Equal to, Boolean == returns 1 if the left and right side are equal.

Left expression == Right expression

Not equal to, Boolean != returns 1 if the left and right side are not equal.

Left expression != Right expression

Less than, Boolean < returns 1 if the left side is less than the right side.

Left expression < Right expression

Less than or equal to, Boolean <= returns 1 if the left side is less than or equal to the right side.

Left expression <= Right expression

Greater than, Boolean > returns 1 if the left side is greater than the right side.

Left expression > Right expression

Greater than or equal to, Boolean >= returns 1 if the left side is greater than or equal to the right side.

Left expression >= Right expression

Logic

Logical operators generally perform true/false operations. S3 uses the following logical operators:

Binary

Binary logical operators operate on two expressions.

Logical AND, Boolean && returns 1 if the left and right side evaluate to true or returns 0 otherwise.

Left expression && Right expression

Logical OR, Boolean || returns 1 if the left side evaluates to true, the right side evaluates to true, or both evaluate to true; or returns 0 otherwise.

Left expression || Right expression

Bamboo, ||| is actually a shortcut for a particularly common case of the ?? ternary operator. It returns the value on the left if it is set; otherwise, it returns the value on the right regardless of its value.

Left expression ||| Right expression

This is equivalent to

Left expression ?? Left expression : Right expression

Ternary

Ternary logical operators operate on three expressions and S3 has two ternary operators.

Logical ternary operator, ? evaluates the left expression for a test that is greater than 0 (numerically) or for a string that has length and is not 0. Otherwise, it evaluates the right expression. For this reason, the test is usually a logical Boolean expression that returns 0 or 1, guaranteed.

test ? Left expression : Right expression

Existential ternary operator, ?? evaluates the left expression for a test that has a value that is not the empty string. Otherwise, it evaluates the right expression.

test ?? Left expression : Right expression

Note:

test ?? test : Right expression

Is equivalent to:

test ||| Right expression

Count

The results of a walk, #count walks the specified OID and returns the count of the occurrences of an OID . This does not resolve the OID in the manner that other naked OIDs are resolved to get the OID value. This #count resolves the OID count immediately, unlike the way an OID is resolved via an OID walk.

Example: To count the number of CPUs on a Linux device to determine what the maximum CPU utilization could be: net-snmp returns up to 800% utilization for a box with eight CPUs.

#count OID

Example:

#count .1.3.6.1.2.1.25.3.3.1.2

Can evaluate to 8.

Conversion

Since OIDs may be indexed by numbers, strings, or variably-sized components, S3 uses conversion operators that operate on a single expression.

Conversion from OID

OID-to-ASCII-string (with length), $s converts the expression to an ASCII string.

$s Expression

The expression should be an OID with the following format:

n.ASCII 1.ASCII 2.....ASCII n

Example:

$s '5.72.101.108.108.111'

Evaluates to Hello.

OID-to-ASCII-string (no length), $S converts the expression to an ASCII string.

$S Expression

The expression should be an OID with the following format:

ASCII 1.ASCII 2

Example:

$S '72.101.108.108.111'

Evaluates to Hello.

OID-to-numbers (with length), $v converts the expression to a string.

$v Expression

The expression should be an OID with the following format:

n.Number 1.Number 2.....Number n

Example:

$v '4.192.168.0.1'

Evaluates to 192.168.0.1.

OID-to-numbers (no length), $V Identity operation; the value should be the same as the expression.

$V Expression

This converts the expression to a string. The expression should be an OID with the following format:

Number 1.Number 2.

Example:

$V '192.168.0.1'

Evaluates to 192.168.0.1.

Conversion to OID

String-to-OID (with length), #s converts the expression to an OID with the length prefixed. The expression should be ASCII text.

#s Expression

Example:

#s 'Hello'

Evaluates to 5.72.101.108.108.111.

String-to-OID (no length), $s converts the expression to a string with no length information. The expression should be ASCII text.

#S Expression

Example:

#S 'Hello'

Evaluates to 72.101.108.108.111.

Numbers-to-OID (with length), #v converts the expression to an OID with the length prefixed. The expression should be text consisting of numbers separated by "."s.

#v Expression

Example:

#v '192.168.0.1'

Evaluates to 4.192.168.0.1.

Numbers-to-OID (no length), #V Identity operation; the value should be the same as the expression converts the expression to an OID with no length information. The expression should be text consisting of numbers separated by "."s.

#V Expression

Example:

#V '192.168.0.1'

Evaluates to 192.168.0.1.

Grouping

Parameters to the conversion operators should be enclosed in parentheses to avoid confusion.

To get the OID index representation of the text 37 (which is 2.51.55), you can try:

#s 1 + 2 3 + 4

However, the #s only applies to the 1 which yields 1.49. (49 is ASCII for 1); the value of that is added to 2 (1.49 + 2 = 3.49), which is then concatenated with 7 (to yield 3.497). You must use parentheses:

#s ( 1 + 2 3 + 4 )

Evaluates to 2.51.55 (which, as a string, is 37).

Logic

The following examples demonstrate Boolean logic.

1. [bothXandY] = `[x]` && `[y]`;

2. [eitherXorYorBoth] = `[x]` || `[y]`;

3. [eitherXorY] = ( `[x]` && (`[y]` ? 0 : 1) ) || ( `[y]` && (`[x]` ? 0 : 1) );

4. [notX] = `[x]` ? 0 : 1;

The following example selects the value of ifName if it is present, or the value of ifDescr otherwise.

[bamboo] = ifName ||| ifDescr;

The following examples demonstrate the use of the ternary operator.

1. [sevenOrEight1] = `[x]` ? 7 : 8;

2. [sevenOrEight2] = `[x]` ? 6 + 1 : 2 * 2 + 4;

Conversion

The following examples convert the text CPU into an OID index. The ASCII value for C=67, P=80, and U=85.

#s 'CPU'

The result of this is "3.67.80.85".

#S 'CPU'

The result of this is 67.80.85 (no length prefix).

The following examples convert the OID indexes specified into strings.

$s '3.67.80.85'

The result of this is CPU.

$S '67.80.85'

The result of this is also CPU.

VACM Entry

The Net-SNMP agent supports the NET-SNMP-VACM-MIB, which provides some information about Net-SNMP's View Access Control Model.

The following is a sample walk of nsVacmAccessEntry (.1.3.6.1.4.1.8072.1.9.1.1):

1. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpcomm1"."".0.noAuthNoPriv."read"

2. = INTEGER: prefix(2)

3. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpcomm1"."".0.noAuthNoPriv."write"

4. = INTEGER: prefix(2)

5. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpcomm1"."".0.noAuthNoPriv."notify"

6. = INTEGER: prefix(2)

7. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpsnmpUser"."".3.authNoPriv."read"

8. = INTEGER: prefix(2)

9. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpsnmpUser"."".3.authNoPriv."write"

10. = INTEGER: prefix(2)

11. NET-SNMP-VACM-MIB::nsVacmContextMatch."grpsnmpUser"."".3.authNoPriv."notify"

12. = INTEGER: prefix(2)

13. NET-SNMP-VACM-MIB::nsVacmViewName."grpcomm1"."".0.noAuthNoPriv."read"

14. = STRING: all

15. NET-SNMP-VACM-MIB::nsVacmViewName."grpcomm1"."".0.noAuthNoPriv."write"

16. = STRING: none

17. NET-SNMP-VACM-MIB::nsVacmViewName."grpcomm1"."".0.noAuthNoPriv."notify"

18. = STRING: none

19. NET-SNMP-VACM-MIB::nsVacmViewName."grpsnmpUser"."".3.authNoPriv."read"

20. = STRING: all

21. NET-SNMP-VACM-MIB::nsVacmViewName."grpsnmpUser"."".3.authNoPriv."write"

22. = STRING: all

23. NET-SNMP-VACM-MIB::nsVacmViewName."grpsnmpUser"."".3.authNoPriv."notify"

24. = STRING: all

25. NET-SNMP-VACM-MIB::nsVacmStorageType."grpcomm1"."".0.noAuthNoPriv."read"

26. = INTEGER: permanent(4)

27. NET-SNMP-VACM-MIB::nsVacmStorageType."grpcomm1"."".0.noAuthNoPriv."write"

28. = INTEGER: permanent(4)

29. NET-SNMP-VACM-MIB::nsVacmStorageType."grpcomm1"."".0.noAuthNoPriv."notify"

30. = INTEGER: permanent(4)

31. NET-SNMP-VACM-MIB::nsVacmStorageType."grpsnmpUser"."".3.authNoPriv."read"

32. = INTEGER: permanent(4)

33. NET-SNMP-VACM-MIB::nsVacmStorageType."grpsnmpUser"."".3.authNoPriv."write"

34. = INTEGER: permanent(4)

35. NET-SNMP-VACM-MIB::nsVacmStorageType."grpsnmpUser"."".3.authNoPriv."notify"

36. = INTEGER: permanent(4)

37. NET-SNMP-VACM-MIB::nsVacmStatus."grpcomm1"."".0.noAuthNoPriv."read"

38. = INTEGER: active(1)

39. NET-SNMP-VACM-MIB::nsVacmStatus."grpcomm1"."".0.noAuthNoPriv."write"

40. = INTEGER: active(1)

41. NET-SNMP-VACM-MIB::nsVacmStatus."grpcomm1"."".0.noAuthNoPriv."notify"

42. = INTEGER: active(1)

43. NET-SNMP-VACM-MIB::nsVacmStatus."grpsnmpUser"."".3.authNoPriv."read"

44. = INTEGER: active(1)

45. NET-SNMP-VACM-MIB::nsVacmStatus."grpsnmpUser"."".3.authNoPriv."write"

46. = INTEGER: active(1)

47. NET-SNMP-VACM-MIB::nsVacmStatus."grpsnmpUser"."".3.authNoPriv."notify"

48. = INTEGER: active(1)

And with numeric OIDs:

1. .1.3.6.1.4.1.8072.1.9.1.1.2.8.103.114.112.99.111.109.109.49.0.0.1.4.114.101.97.100

2. = INTEGER: prefix(2)

3. .1.3.6.1.4.1.8072.1.9.1.1.2.8.103.114.112.99.111.109.109.49.0.0.1.5.119.114.105.116.101

4. = INTEGER: prefix(2)

5. .1.3.6.1.4.1.8072.1.9.1.1.2.8.103.114.112.99.111.109.109.49.0.0.1.6.110.111.116.105.102.121

6. = INTEGER: prefix(2)

7. .1.3.6.1.4.1.8072.1.9.1.1.2.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.4.114.101.97.100

8. = INTEGER: prefix(2)

9. .1.3.6.1.4.1.8072.1.9.1.1.2.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.5.119.114.105.116.101

10. = INTEGER: prefix(2)

11. .1.3.6.1.4.1.8072.1.9.1.1.2.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.6.110.111.116.105.102.121

12. = INTEGER: prefix(2)

13. .1.3.6.1.4.1.8072.1.9.1.1.3.8.103.114.112.99.111.109.109.49.0.0.1.4.114.101.97.100

14. = STRING: all

15. .1.3.6.1.4.1.8072.1.9.1.1.3.8.103.114.112.99.111.109.109.49.0.0.1.5.119.114.105.116.101

16. = STRING: none

17. .1.3.6.1.4.1.8072.1.9.1.1.3.8.103.114.112.99.111.109.109.49.0.0.1.6.110.111.116.105.102.121

18. = STRING: none

19. .1.3.6.1.4.1.8072.1.9.1.1.3.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.4.114.101.97.100

20. = STRING: all

21. .1.3.6.1.4.1.8072.1.9.1.1.3.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.5.119.114.105.116.101

22. = STRING: all

23. .1.3.6.1.4.1.8072.1.9.1.1.3.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.6.110.111.116.105.102.121

24. = STRING: all

25. .1.3.6.1.4.1.8072.1.9.1.1.4.8.103.114.112.99.111.109.109.49.0.0.1.4.114.101.97.100

26. = INTEGER: permanent(4)

27. .1.3.6.1.4.1.8072.1.9.1.1.4.8.103.114.112.99.111.109.109.49.0.0.1.5.119.114.105.116.101

28. = INTEGER: permanent(4)

29. .1.3.6.1.4.1.8072.1.9.1.1.4.8.103.114.112.99.111.109.109.49.0.0.1.6.110.111.116.105.102.121

30. = INTEGER: permanent(4)

31. .1.3.6.1.4.1.8072.1.9.1.1.4.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.4.114.101.97.100

32. = INTEGER: permanent(4)

33. .1.3.6.1.4.1.8072.1.9.1.1.4.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.5.119.114.105.116.101

34. = INTEGER: permanent(4)

35. .1.3.6.1.4.1.8072.1.9.1.1.4.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.6.110.111.116.105.102.121

36. = INTEGER: permanent(4)

37. .1.3.6.1.4.1.8072.1.9.1.1.5.8.103.114.112.99.111.109.109.49.0.0.1.4.114.101.97.100

38. = INTEGER: active(1)

39. .1.3.6.1.4.1.8072.1.9.1.1.5.8.103.114.112.99.111.109.109.49.0.0.1.5.119.114.105.116.101

40. = INTEGER: active(1)

41. .1.3.6.1.4.1.8072.1.9.1.1.5.8.103.114.112.99.111.109.109.49.0.0.1.6.110.111.116.105.102.121

42. = INTEGER: active(1)

43. .1.3.6.1.4.1.8072.1.9.1.1.5.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.4.114.101.97.100

44. = INTEGER: active(1)

45. .1.3.6.1.4.1.8072.1.9.1.1.5.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.5.119.114.105.116.101

46. = INTEGER: active(1)

47. .1.3.6.1.4.1.8072.1.9.1.1.5.11.103.114.112.115.110.109.112.85.115.101.114.0.3.2.6.110.111.116.105.102.121

48. = INTEGER: active(1)

Now, let us pretend that we are concerned with the "nsVacmStatus" OID for each of these entries.

Indexing

S3 has two options to properly index entries.

1. S3 can choose a variable-length index (with no length prefix). However, this provides S3 no insight as to the components of the index. There are no OIDs available to determine a proper name for any of the entries to enter into the system as objects.

2. S3 can explicitly define each index component, which allows S3 to reference each component individually to properly name objects.

The index composed of the following types of fields.

Example:

"grpcomm1"."".0.noAuthNoPriv."read"

• String, (e.g., grpcomm1) - According to the MIB is the name of the group for this entry.

• String, (e.g., "") - According to the MIB is the prefix that a name must match to gain access rights.

• Integer, (e.g., 0) - According to the MIB is the security model in use. This roughly corresponds with the SNMP version (where 0 = any).

• Integer, (e.g., noAuthNoPriv, which is, 1) - According to the MIB is the minimum level of security required to gain access rights.

• String, (e.g., read) - According to the MIB is the type of processing to which to apply the specified view.

Given that, S3 has the following information:

• [INDEX] is 8.103.114.112.99.111.109.109.49.0.0.1.4.114.101.97.100.
• [INDEX]{0} is 8.103.114.112.99.111.109.109.49.
• [INDEX]{1} is 0.
• [INDEX]{2} is 0.
• [INDEX]{3} is 1.
• [INDEX]{4} is 4.114.101.97.100.

Synthetic indicators

Indicator expressions are unique because they are handled in a two pass system. The SNMP poller does not implement S3; it implements a simple mathematical library. Any OIDs present in the data that is passed to the poller must be fully expanded with their index information. To accomplish this, two passes are used on the indicator expression.

The text-conversion functions of S3 does not work in either pass.

First pass

The first pass is an expansion pass. It expands any OID encountered by adding the full index value to the end of it. This is equivalent to having every OID end in ".[INDEX]". The result of this pass is saved (no real values should be generated).

Second pass

The second pass then evaluates (normally) the results of the first pass. If this pass results in a numeric value, then the indicator is presumed to exist. The results of the first pass are stored for use by the poller.

It is important to use standard mathematical expressions (and not the extra S3 operations) to perform indicator expressions. These expressions must conform to normal mathematical rules (for example, you cannot have two expressions next to each other with no joining operator). These expressions may include the following operators:

/ + -

And the following grouping symbols:

( )

Note: It is possible to get around the OID expansion in the first pass. The entire results of the evaluated first pass are passed to the second pass. Any text in the first pass does not have its quotes in the second pass. Thus, an OID may be quoted and used exactly as quoted in the second pass. The whole first pass could be quoted to prevent S3 from taking any intelligent action.

Example

To have every interface report, as an indicator, the total number of interfaces on the device (multiplied by 10), the following indicator expression does not work:

ifNumber.0 * 10

"ifNumber.0" is expanded with the default index, which in this case could be ".2", for example (yielding "ifNumber.0.2", which is not the desired outcome):

ifNumber.0.2 * 10

However, the following tricks the system into accepting the OID:

`ifNumber.0` * 10

This yields:

ifNumber.0 * 10

This is the desired outcome.

Summary of the two-pass system

1. Pass 1

   1. OIDs are expanded.

   2. Text is unquoted.

2. Pass 2

   1. Pass 1 is evaluated.

Notes:

• Do not use text-conversion functions.