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Configuring SNMP Remote Operations

SNMP Remote Operations Overview

A SNMP remote operation is any process on the router that can be controlled remotely using SNMP. Junos OS currently provides support for two SNMP remote operations: the Ping MIB and Traceroute MIB, defined in RFC 2925. Using these MIBs, an SNMP client in the network management system (NMS) can:

  • Start a series of operations on a router

  • Receive notification when the operations are complete

  • Gather the results of each operation

Junos OS also provides extended functionality to these MIBs in the Juniper Networks enterprise-specific extensions jnxPingMIB and jnxTraceRouteMIB. For more information about jnxPingMIB and jnxTraceRouteMIB, see PING MIB and Traceroute MIB.

This topic covers the following sections:

SNMP Remote Operation Requirements

To use SNMP remote operations, you should be experienced with SNMP conventions. You must also configure Junos OS to allow the use of the remote operation MIBs.

Before starting the Ping MIB, see Starting a Ping Test.

Before starting the Traceroute MIB, see Starting a Traceroute Test.

Setting SNMP Views

All remote operation MIBs supported by Junos OS require that the SNMP clients have read-write privileges. The default SNMP configuration of Junos OS does not provide clients with a community string with such privileges.

To set read-write privileges for an SNMP community string, include the following statements at the [edit snmp] hierarchy level:

Example: Setting SNMP Views

To create a community named remote-community that grants SNMP clients read-write access to the Ping MIB, jnxPing MIB, Traceroute MIB, and jnxTraceRoute MIB, include the following statements at the [edit snmp] hierarchy level:

For more information about the community statement, see Configuring SNMP Communities and community (SNMP).

For more information about the view statement, see Configuring MIB Views, view (SNMP Community), and view (Configuring a MIB View).

Setting Trap Notification for Remote Operations

In addition to configuring the remote operations MIB for trap notification, you must also configure Junos OS. You must specify a target host for remote operations traps.

To configure trap notification for SNMP remote operations, include the categories and targets statements at the [edit snmp trap-group group-name] hierarchy level:

Example: Setting Trap Notification for Remote Operations

Specify 172.17.12.213 as a target host for all remote operation traps:

For more information about trap groups, see Configuring SNMP Trap Groups.

Using Variable-Length String Indexes

All tabular objects in the remote operations MIBs supported by Junos OS are indexed by two variables of type SnmpAdminString. For more information about SnmpAdminString, see RFC 2571.

Junos OS does not handle SnmpAdminString any differently from the octet string variable type. However, the indexes are defined as variable length. When a variable length string is used as an index, the length of the string must be included as part of the object identifier (OID).

Example: Set Variable-Length String Indexes

To reference the pingCtlTargetAddress variable of a row in pingCtlTable where pingCtlOwnerIndex is bob and pingCtlTestName is test, use the following object identifier (OID):

For more information about the definition of the Ping MIB, see RFC 2925.

Enabling Logging

The SNMP error code returned in response to SNMP requests can only provide a generic description of the problem. The error descriptions logged by the remote operations process can often provide more detailed information about the problem and help you to solve the problem faster. This logging is not enabled by default. To enable logging, include the flag general statement at the [edit snmp traceoptions] hierarchy level:

If the remote operations process receives an SNMP request that it cannot accommodate, the error is logged in the /var/log/rmopd file. To monitor this log file, issue the monitor start rmopd command in operational mode of the command-line interface (CLI).

Using the Ping MIB for Remote Monitoring Devices Running Junos OS

A ping test is used to determine whether packets sent from the local host reach the designated host and are returned. If the designated host can be reached, the ping test provides the approximate round-trip time for the packets. Ping test results are stored in pingResultsTable and pingProbeHistoryTable.

RFC 2925 is the authoritative description of the Ping MIB in detail and provides the ASN.1 MIB definition of the Ping MIB.

Starting a Ping Test

Use this topic to launch an ICMP ping test. There are two ways to start a ping test: using multiple Set protocol data units (PDUs) or using a single Set PDU.

Before You Begin

Before you start a ping test, configure a Ping MIB view. This allows SNMP Set requests on pingMIB. For more information, see Configuring MIB Views.

Starting in Junos OS Release 17.2X75-D100, you must configure RPM before starting an ICMP ping. Configure RPM using the edit services rpm command.

Starting a Ping Test

To start a ping test, create a row in pingCtlTable and set pingCtlAdminStatus to enabled. The minimum information that must be specified before setting pingCtlAdminStatus to enabled is:

  • pingCtlOwnerIndexSnmpAdminString

  • pingCtlTestNameSnmpAdminString

  • pingCtlTargetAddressInetAddress

  • pingCtlTargetAddressTypeInetAddressType

  • pingCtlRowStatusRowStatus

For all other values, defaults are chosen unless otherwise specified. pingCtlOwnerIndex and pingCtlTestName are used as the index, so their values are specified as part of the object identifier (OID). To create a row, set pingCtlRowStatus to createAndWait or createAndGo on a row that does not already exist. A value of active for pingCtlRowStatus indicates that all necessary information has been supplied and the test can begin; pingCtlAdminStatus can be set to enabled. An SNMP Set request that sets pingCtlRowStatus to active will fail if the necessary information in the row is not specified or is inconsistent.

For information about how to configure a view, see Setting SNMP Views.

Read the following sections for how to order the variables.

Using Multiple Set PDUs

You can use multiple Set request PDUs (multiple PDUs, with one or more varbinds each) and set the following variables in this order to start the test:

  • pingCtlRowStatus to createAndWait

  • All appropriate test variables

  • pingCtlRowStatus to active

    Junos OS now verifies that all necessary information to run a test has been specified.

  • pingCtlAdminStatus to enabled

Using a Single Set PDU

You can use a single Set request PDU (one PDU, with multiple varbinds) to set the following variables to start the test:

  • pingCtlRowStatus to createAndGo

  • All appropriate test variables

  • pingCtlAdminStatus to enabled

Monitoring a Running Ping Test

When pingCtlAdminStatus is successfully set to enabled, the following is done before the acknowledgment of the SNMP Set request is sent back to the client:

  • pingResultsEntry is created if it does not already exist.

  • pingResultsOperStatus transitions to enabled.

For more information, see the following sections:

pingResultsTable

While the test is running, pingResultsEntry keeps track of the status of the test. The value of pingResultsOperStatus is enabled while the test is running and disabled when it has stopped.

The value of pingCtlAdminStatus remains enabled until you set it to disabled. Thus, to get the status of the test, you must examine pingResultsOperStatus.

The pingCtlFrequency variable can be used to schedule many tests for one pingCtlEntry. After a test ends normally (you did not stop the test) and the pingCtlFrequency number of seconds has elapsed, the test is started again just as if you had set pingCtlAdminStatus to enabled. If you intervene at any time between repeated tests (you set pingCtlAdminStatus to disabled or pingCtlRowStatus to notInService), the repeat feature is disabled until another test is started and ends normally. A value of 0 for pingCtlFrequency indicates this repeat feature is not active.

pingResultsIpTgtAddr and pingResultsIpTgtAddrType are set to the value of the resolved destination address when the value of pingCtlTargetAddressType is dns. When a test starts successfully and pingResultsOperStatus transitions to enabled:

  • pingResultsIpTgtAddr is set to null-string.

  • pingResultsIpTgtAddrType is set to unknown.

pingResultsIpTgtAddr and pingResultsIpTgtAddrType are not set until pingCtlTargetAddress can be resolved to a numeric address. To retrieve these values, poll pingResultsIpTgtAddrType for any value other than unknown after successfully setting pingCtlAdminStatus to enabled.

At the start of a test, pingResultsSentProbes is initialized to 1 and the first probe is sent. pingResultsSentProbes increases by 1 each time a probe is sent.

As the test runs, every pingCtlTimeOut seconds, the following occur:

  • pingProbeHistoryStatus for the corresponding pingProbeHistoryEntry in pingProbeHistoryTable is set to requestTimedOut.

  • A pingProbeFailed trap is generated, if necessary.

  • An attempt is made to send the next probe.

    Note:

    No more than one outstanding probe exists for each test.

For every probe, you can receive one of the following results:

  • The target host acknowledges the probe with a response.

  • The probe times out; there is no response from the target host acknowledging the probe.

  • The probe could not be sent.

Each probe result is recorded in pingProbeHistoryTable. For more information about pingProbeHistoryTable, see pingProbeHistoryTable.

When a response is received from the target host acknowledging the current probe:

  • pingResultsProbeResponses increases by 1.

  • The following variables are updated:

    • pingResultsMinRtt—Minimum round-trip time

    • pingResultsMaxRtt—Maximum round-trip time

    • pingResultsAverageRtt—Average round-trip time

    • pingResultsRttSumOfSquares—Sum of squares of round-trip times

    • pingResultsLastGoodProbe—Timestamp of the last response

      Note:

      Only probes that result in a response from the target host contribute to the calculation of the round-trip time (RTT) variables.

When a response to the last probe is received or the last probe has timed out, the test is complete.

pingProbeHistoryTable

An entry in pingProbeHistoryTable (pingProbeHistoryEntry) represents a probe result and is indexed by three variables:

  • The first two variables, pingCtlOwnerIndex and pingCtlTestName, are the same ones used for pingCtlTable, which identifies the test.

  • The third variable, pingProbeHistoryIndex, is a counter to uniquely identify each probe result.

The maximum number of pingProbeHistoryTable entries created for a given test is limited by pingCtlMaxRows. If pingCtlMaxRows is set to 0, no pingProbeHistoryTable entries are created for that test.

Each time a probe result is determined, a pingProbeHistoryEntry is created and added to pingProbeHistoryTable. pingProbeHistoryIndex of the new pingProbeHistoryEntry is 1 greater than the last pingProbeHistoryEntry added to pingProbeHistoryTable for that test. pingProbeHistoryIndex is set to 1 if this is the first entry in the table. The same test can be run multiple times, so this index keeps growing.

If pingProbeHistoryIndex of the last pingProbeHistoryEntry added is 0xFFFFFFFF, the next pingProbeHistoryEntry added has pingProbeHistoryIndex set to 1.

The following are recorded for each probe result:

  • pingProbeHistoryResponse—Time to live (TTL)

  • pingProbeHistoryStatus—What happened and why

  • pingProbeHistoryLastRC—Return code (RC) value of ICMP packet

  • pingProbeHistoryTime—Timestamp when probe result was determined

When a probe cannot be sent, pingProbeHistoryResponse is set to 0. When a probe times out, pingProbeHistoryResponse is set to the difference between the time when the probe was discovered to be timed out and the time when the probe was sent.

Generating Traps

For any trap to be generated, the appropriate bit of pingCtlTrapGeneration must be set. You must also configure a trap group to receive remote operations. A trap is generated under the following conditions:

  • A pingProbeFailed trap is generated every time pingCtlTrapProbeFailureFilter number of consecutive probes fail during the test.

  • A pingTestFailed trap is generated when the test completes and at least pingCtlTrapTestFailureFilter number of probes fail.

  • A pingTestCompleted trap is generated when the test completes and fewer than pingCtlTrapTestFailureFilter probes fail.

    Note:

    A probe is considered a failure when pingProbeHistoryStatus of the probe result is anything besides responseReceived.

For information about how to configure a trap group to receive remote operations, see Configuring SNMP Trap Groups and Example: Setting Trap Notification for Remote Operations.

Gathering Ping Test Results

You can either poll pingResultsOperStatus to find out when the test is complete or request that a trap be sent when the test is complete. For more information about pingResultsOperStatus, see pingResultsTable. For more information about Ping MIB traps, see Generating Traps.

The statistics calculated and then stored in pingResultsTable include:

  • pingResultsMinRtt—Minimum round-trip time

  • pingResultsMaxRtt—Maximum round-trip time

  • pingResultsAverageRtt—Average round-trip time

  • pingResultsProbeResponses—Number of responses received

  • pingResultsSentProbes—Number of attempts to send probes

  • pingResultsRttSumOfSquares—Sum of squares of round-trip times

  • pingResultsLastGoodProbe—Timestamp of the last response

You can also consult pingProbeHistoryTable for more detailed information about each probe. The index used for pingProbeHistoryTable starts at 1, goes to 0xFFFFFFFF, and wraps to 1 again.

For example, if pingCtlProbeCount is 15 and pingCtlMaxRows is 5, then upon completion of the first run of this test, pingProbeHistoryTable contains probes like those in Table 1.

Table 1: Results in pingProbeHistoryTable: After the First Ping Test

pingProbeHistoryIndex

Probe Result

11

Result of 11th probe from run 1

12

Result of 12th probe from run 1

13

Result of 13th probe from run 1

14

Result of 14th probe from run 1

15

Result of 15th probe from run 1

Upon completion of the first probe of the second run of this test, pingProbeHistoryTable will contain probes like those in Table 2.

Table 2: Results in pingProbeHistoryTable: After the First Probe of the Second Test

pingProbeHistoryIndex

Probe Result

12

Result of 12th probe from run 1

13

Result of 13th probe from run 1

14

Result of 14th probe from run 1

15

Result of 15th probe from run 1

16

Result of 1st probe from run 2

Upon completion of the second run of this test, pingProbeHistoryTable will contain probes like those in Table 3.

Table 3: Results in pingProbeHistoryTable: After the Second Ping Test

pingProbeHistoryIndex

Probe Result

26

Result of 11th probe from run 2

27

Result of 12th probe from run 2

28

Result of 13th probe from run 2

29

Result of 14th probe from run 2

30

Result of 15th probe from run 2

History entries can be deleted from the MIB in two ways:

  • More history entries for a given test are added and the number of history entries exceeds pingCtlMaxRows. The oldest history entries are deleted to make room for the new ones.

  • You delete the entire test by setting pingCtlRowStatus to destroy.

Stopping a Ping Test

To stop an active test, set pingCtlAdminStatus to disabled. To stop the test and remove its pingCtlEntry, pingResultsEntry, and any pingHistoryEntry objects from the MIB, set pingCtlRowStatus to destroy.

Interpreting Ping Variables

This section clarifies the ranges for the following variables that are not explicitly specified in the Ping MIB:

  • pingCtlDataSize—The value of this variable represents the total size of the payload (in bytes) of an outgoing probe packet. This payload includes the timestamp (8 bytes) that is used to time the probe. This is consistent with the definition of pingCtlDataSize (maximum value of 65,507) and the standard ping application.

    If the value of pingCtlDataSize is between 0 and 8 inclusive, it is ignored and the payload is 8 bytes (the timestamp). The Ping MIB assumes all probes are timed, so the payload must always include the timestamp.

    For example, if you wish to add an additional 4 bytes of payload to the packet, you must set pingCtlDataSize to 12.

  • pingCtlDataFill—The first 8 bytes of the data segment of the packet is for the timestamp. After that, the pingCtlDataFill pattern is used in repetition. The default pattern (when pingCtlDataFill is not specified) is (00, 01, 02, 03 ... FF, 00, 01, 02, 03 ... FF, ...).

  • pingCtlMaxRows—The maximum value is 255.

  • pingMaxConcurrentRequests—The maximum value is 500.

  • pingCtlTrapProbeFailureFilter and pingCtlTrapTestFailureFilter—A value of 0 for pingCtlTrapProbeFailureFilter or pingCtlTrapTestFailureFilter is not well defined by the Ping MIB. If pingCtlTrapProbeFailureFilter is 0, pingProbeFailed traps will not be generated for the test under any circumstances. If pingCtlTrapTestFailureFilter is 0, pingTestFailed traps will not be generated for the test under any circumstances.

Using the Traceroute MIB for Remote Monitoring Devices Running Junos OS

A traceroute test approximates the path packets take from the local host to the remote host.

RFC 2925 is the authoritative description of the Traceroute MIB in detail and provides the ASN.1 MIB definition of the Traceroute MIB.

Starting a Traceroute Test

Before you start a traceroute test, configure a Traceroute MIB view. This allows SNMP Set requests on tracerouteMIB. To start a test, create a row in traceRouteCtlTable and set traceRouteCtlAdminStatus to enabled. You must specify at least the following before setting traceRouteCtlAdminStatus to enabled:

  • traceRouteCtlOwnerIndexSnmpAdminString

  • traceRouteCtlTestNameSnmpAdminString

  • traceRouteCtlTargetAddressInetAddress

  • traceRouteCtlRowStatusRowStatus

For all other values, defaults are chosen unless otherwise specified. traceRouteCtlOwnerIndex and traceRouteCtlTestName are used as the index, so their values are specified as part of the OID. To create a row, set traceRouteCtlRowStatus to createAndWait or createAndGo on a row that does not already exist. A value of active for traceRouteCtlRowStatus indicates that all necessary information has been specified and the test can begin; traceRouteCtlAdminStatus can be set to enabled. An SNMP Set request that sets traceRouteCtlRowStatus to active will fail if the necessary information in the row is not specified or is inconsistent. For information about how to configure a view, see Setting SNMP Views.

There are two ways to start a traceroute test:

Using Multiple Set PDUs

You can use multiple Set request PDUs (multiple PDUs, with one or more varbinds each) and set the following variables in this order to start the test:

  • traceRouteCtlRowStatus to createAndWait

  • All appropriate test variables

  • traceRouteCtlRowStatus to active

    The Junos OS now verifies that all necessary information to run a test has been specified.

  • traceRouteCtlAdminStatus to enabled

Using a Single Set PDU

You can use a single Set request PDU (one PDU, with multiple varbinds) to set the following variables to start the test:

  • traceRouteCtlRowStatus to createAndGo

  • All appropriate test variables

  • traceRouteCtlAdminStatus to enabled

Monitoring a Running Traceroute Test

When traceRouteCtlAdminStatus is successfully set to enabled, the following is done before the acknowledgment of the SNMP Set request is sent back to the client:

  • traceRouteResultsEntry is created if it does not already exist.

  • traceRouteResultsOperStatus transitions to enabled.

For more information, see the following sections:

traceRouteResultsTable

While the test is running, this traceRouteResultsTable keeps track of the status of the test. The value of traceRouteResultsOperStatus is enabled while the test is running and disabled when it has stopped.

The value of traceRouteCtlAdminStatus remains enabled until you set it to disabled. Thus, to get the status of the test, you must examine traceRouteResultsOperStatus.

The traceRouteCtlFrequency variable can be used to schedule many tests for one traceRouteCtlEntry. After a test ends normally (you did not stop the test) and traceRouteCtlFrequency number of seconds has elapsed, the test is started again just as if you had set traceRouteCtlAdminStatus to enabled. If you intervene at any time between repeated tests (you set traceRouteCtlAdminStatus to disabled or traceRouteCtlRowStatus to notInService), the repeat feature is disabled until another test is started and ends normally. A value of 0 for traceRouteCtlFrequency indicates this repeat feature is not active.

traceRouteResultsIpTgtAddr and traceRouteResultsIpTgtAddrType are set to the value of the resolved destination address when the value of traceRouteCtlTargetAddressType is dns. When a test starts successfully and traceRouteResultsOperStatus transitions to enabled:

  • traceRouteResultsIpTgtAddr is set to null-string.

  • traceRouteResultsIpTgtAddrType is set to unknown.

traceRouteResultsIpTgtAddr and traceRouteResultsIpTgtAddrType are not set until traceRouteCtlTargetAddress can be resolved to a numeric address. To retrieve these values, poll traceRouteResultsIpTgtAddrType for any value other than unknown after successfully setting traceRouteCtlAdminStatus to enabled.

At the start of a test, traceRouteResultsCurHopCount is initialized to traceRouteCtlInitialTtl, and traceRouteResultsCurProbeCount is initialized to 1. Each time a probe result is determined, traceRouteResultsCurProbeCount increases by 1. While the test is running, the value of traceRouteResultsCurProbeCount reflects the current outstanding probe for which results have not yet been determined.

The traceRouteCtlProbesPerHop number of probes is sent for each time-to-live (TTL) value. When the result of the last probe for the current hop is determined, provided that the current hop is not the destination hop, traceRouteResultsCurHopCount increases by 1, and traceRouteResultsCurProbeCount resets to 1.

At the start of a test, if this is the first time this test has been run for this traceRouteCtlEntry, traceRouteResultsTestAttempts and traceRouteResultsTestSuccesses are initialized to 0.

At the end of each test execution, traceRouteResultsOperStatus transitions to disabled, and traceRouteResultsTestAttempts increases by 1. If the test was successful in determining the full path to the target, traceRouteResultsTestSuccesses increases by 1, and traceRouteResultsLastGoodPath is set to the current time.

traceRouteProbeResultsTable

Each entry in traceRouteProbeHistoryTable is indexed by five variables:

  • The first two variables, traceRouteCtlOwnerIndex and traceRouteCtlTestName, are the same ones used for traceRouteCtlTable and to identify the test.

  • The third variable, traceRouteProbeHistoryIndex, is a counter, starting from 1 and wrapping at FFFFFFFF. The maximum number of entries is limited by traceRouteCtlMaxRows.

  • The fourth variable, traceRouteProbeHistoryHopIndex, indicates which hop this probe is for (the actual time-to-live or TTL value). Thus, the first traceRouteCtlProbesPerHop number of entries created when a test starts have a value of traceRouteCtlInitialTtl for traceRouteProbeHistoryHopIndex.

  • The fifth variable, traceRouteProbeHistoryProbeIndex, is the probe for the current hop. It ranges from 1 to traceRouteCtlProbesPerHop.

While a test is running, as soon as a probe result is determined, the next probe is sent. A maximum of traceRouteCtlTimeOut seconds elapses before a probe is marked with status requestTimedOut and the next probe is sent. There is never more than one outstanding probe per traceroute test. Any probe result coming back after a probe times out is ignored.

Each probe can:

  • Result in a response from a host acknowledging the probe

  • Time out with no response from a host acknowledging the probe

  • Fail to be sent

Each probe status is recorded in traceRouteProbeHistoryTable with traceRouteProbeHistoryStatus set accordingly.

Probes that result in a response from a host record the following data:

  • traceRouteProbeHistoryResponse—Round-trip time (RTT)

  • traceRouteProbeHistoryHAddrType—The type of HAddr (next argument)

  • traceRouteProbeHistoryHAddr—The address of the hop

All probes, regardless of whether a response for the probe is received, have the following recorded:

  • traceRouteProbeHistoryStatus—What happened and why

  • traceRouteProbeHistoryLastRC—Return code (RC) value of the ICMP packet

  • traceRouteProbeHistoryTime—Timestamp when the probe result was determined

When a probe cannot be sent, traceRouteProbeHistoryResponse is set to 0. When a probe times out, traceRouteProbeHistoryResponse is set to the difference between the time when the probe was discovered to be timed out and the time when the probe was sent.

traceRouteHopsTable

Entries in traceRouteHopsTable are indexed by three variables:

  • The first two, traceRouteCtlOwnerIndex and traceRouteCtlTestName, are the same ones used for traceRouteCtlTable and identify the test.

  • The third variable, traceRouteHopsHopIndex, indicates the current hop, which starts at 1 (not traceRouteCtlInitialTtl).

When a test starts, all entries in traceRouteHopsTable with the given traceRouteCtlOwnerIndex and traceRouteCtlTestName are deleted. Entries in this table are only created if traceRouteCtlCreateHopsEntries is set to true.

A new traceRouteHopsEntry is created each time the first probe result for a given TTL is determined. The new entry is created whether or not the first probe reaches a host. The value of traceRouteHopsHopIndex is increased by 1 for this new entry.

Note:

Any traceRouteHopsEntry can lack a value for traceRouteHopsIpTgtAddress if there are no responses to the probes with the given TTL.

Each time a probe reaches a host, the IP address of that host is available in the probe result. If the value of traceRouteHopsIpTgtAddress of the current traceRouteHopsEntry is not set, then the value of traceRouteHopsIpTgtAddress is set to this IP address. If the value of traceRouteHopsIpTgtAddress of the current traceRouteHopsEntry is the same as the IP address, then the value does not change. If the value of traceRouteHopsIpTgtAddress of the current traceRouteHopsEntry is different from this IP address, indicating a path change, a new traceRouteHopsEntry is created with:

  • traceRouteHopsHopIndex variable increased by 1

  • traceRouteHopsIpTgtAddress set to the IP address

    Note:

    A new entry for a test is added to traceRouteHopsTable each time a new TTL value is used or the path changes. Thus, the number of entries for a test may exceed the number of different TTL values used.

When a probe result is determined, the value traceRouteHopsSentProbes of the current traceRouteHopsEntry increases by 1. When a probe result is determined, and the probe reaches a host:

  • The value traceRouteHopsProbeResponses of the current traceRouteHopsEntry is increased by 1.

  • The following variables are updated:

    • traceRouteResultsMinRtt—Minimum round-trip time

    • traceRouteResultsMaxRtt—Maximum round-trip time

    • traceRouteResultsAverageRtt—Average round-trip time

    • traceRouteResultsRttSumOfSquares—Sum of squares of round-trip times

    • traceRouteResultsLastGoodProbe—Timestamp of the last response

      Note:

      Only probes that reach a host affect the round-trip time values.

Generating Traps

For any trap to be generated, the appropriate bit of traceRouteCtlTrapGeneration must be set. You must also configure a trap group to receive remote operations. Traps are generated under the following conditions:

  • traceRouteHopsIpTgtAddress of the current probe is different from the last probe with the same TTL value (traceRoutePathChange).

  • A path to the target could not be determined (traceRouteTestFailed).

A path to the target was determined (traceRouteTestCompleted).

For information about how to configure a trap group to receive remote operations, see Configuring SNMP Trap Groups and SNMP Remote Operations Overview.

Monitoring Traceroute Test Completion

When a test is complete, traceRouteResultsOperStatus transitions from enabled to disabled. This transition occurs in the following situations:

  • The test ends successfully. A probe result indicates that the destination has been reached. In this case, the current hop is the last hop. The rest of the probes for this hop are sent. When the last probe result for the current hop is determined, the test ends.

  • traceRouteCtlMaxTtl threshold is exceeded. The destination is never reached. The test ends after the number of probes with TTL value equal to traceRouteCtlMaxttl have been sent.

  • traceRouteCtlMaxFailures threshold is exceeded. The number of consecutive probes that end with status requestTimedOut exceeds traceRouteCtlMaxFailures.

  • You end the test. You set traceRouteCtlAdminStatus to disabled or delete the row by setting traceRouteCtlRowStatus to destroy.

  • You misconfigured the traceroute test. A value or variable you specified in traceRouteCtlTable is incorrect and will not allow a single probe to be sent. Because of the nature of the data, this error could not be determined until the test was started; that is, until after traceRouteResultsOperStatus transitioned to enabled. When this occurs, one entry is added to traceRouteProbeHistoryTable with traceRouteProbeHistoryStatus set to the appropriate error code.

If traceRouteCtlTrapGeneration is set properly, either the traceRouteTestFailed or traceRouteTestCompleted trap is generated.

Gathering Traceroute Test Results

You can either poll traceRouteResultsOperStatus to find out when the test is complete or request that a trap be sent when the test is complete. For more information about traceResultsOperStatus, see traceRouteResultsTable. For more information about Traceroute MIB traps, see the Generating Traps section in Monitoring a Running Traceroute Test.

Statistics are calculated on a per-hop basis and then stored in traceRouteHopsTable. They include the following for each hop:

  • traceRouteHopsIpTgtAddressType—Address type of host at this hop

  • traceRouteHopsIpTgtAddress—Address of host at this hop

  • traceRouteHopsMinRtt—Minimum round-trip time

  • traceRouteHopsMaxRtt—Maximum round-trip time

  • traceRouteHopsAverageRtt—Average round-trip time

  • traceRouteHopsRttSumOfSquares—Sum of squares of round-trip times

  • traceRouteHopsSentProbes—Number of attempts to send probes

  • traceRouteHopsProbeResponses—Number of responses received

  • traceRouteHopsLastGoodProbe—Timestamp of last response

You can also consult traceRouteProbeHistoryTable for more detailed information about each probe. The index used for traceRouteProbeHistoryTable starts at 1, goes to 0xFFFFFFFF, and wraps to 1 again.

For example, assume the following:

  • traceRouteCtlMaxRows is 10.

  • traceRouteCtlProbesPerHop is 5.

  • There are eight hops to the target (the target being number eight).

  • Each probe sent results in a response from a host (the number of probes sent is not limited by traceRouteCtlMaxFailures).

In this test, 40 probes are sent. At the end of the test, traceRouteProbeHistoryTable would have a history of probes like those in Table 4.

Table 4: traceRouteProbeHistoryTable

HistoryIndex

HistoryHopIndex

HistoryProbeIndex

31

7

1

32

7

2

33

7

3

34

7

4

35

7

5

36

8

1

37

8

2

38

8

3

39

8

4

40

8

5

Stopping a Traceroute Test

To stop an active test, set traceRouteCtlAdminStatus to disabled. To stop a test and remove its traceRouteCtlEntry, traceRouteResultsEntry, traceRouteProbeHistoryEntry, and traceRouteProbeHistoryEntry objects from the MIB, set traceRouteCtlRowStatus to destroy.

Interpreting Traceroute Variables

This topic contains information about the ranges for the following variables that are not explicitly specified in the Traceroute MIB:

  • traceRouteCtlMaxRows—The maximum value for traceRouteCtlMaxRows is 2550. This represents the maximum TTL (255) multiplied by the maximum for traceRouteCtlProbesPerHop (10). Therefore, the traceRouteProbeHistoryTable accommodates one complete test at the maximum values for one traceRouteCtlEntry. Usually, the maximum values are not used and the traceRouteProbeHistoryTable is able to accommodate the complete history for many tests for the same traceRouteCtlEntry.

  • traceRouteMaxConcurrentRequests—The maximum value is 50. If a test is running, it has one outstanding probe. traceRouteMaxConcurrentRequests represents the maximum number of traceroute tests that have traceRouteResultsOperStatus with a value of enabled. Any attempt to start a test with traceRouteMaxConcurrentRequests tests running will result in the creation of one probe with traceRouteProbeHistoryStatus set to maxConcurrentLimitReached and that test will end immediately.

  • traceRouteCtlTable—The maximum number of entries allowed in this table is 100. Any attempt to create a 101st entry will result in a BAD_VALUE message for SNMPv1 and a RESOURCE_UNAVAILABLE message for SNMPv2.

Release History Table
Release
Description
17.2X75-D100
Starting in Junos OS Release 17.2X75-D100, you must configure RPM before starting an ICMP ping.