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Tracing SNMP Activity on a JUNOS Device

Simple Network Management Protocol (SNMP) tracing operations track activity for SNMP agents and record the information in log files. The logged error descriptions provide detailed information to help you solve problems faster.

By default, the JUNOS software does not trace any SNMP activity. If you include the traceoptions statement at the [edit snmp] hierarchy level, the default tracing behavior is the following:

Important activities are logged in files located in the /var/log directory. Each log is named after the SNMP agent that generates it. Currently, the following log files are created in the /var/log directory when the traceoptions statement is used:
- chassisd
- craftd
- ilmid
- mib2d
- rmopd
- serviced
- snmpd
When a trace file named filename reaches its maximum size, it is renamed filename.0, then filename.1, and so on, until the maximum number of trace files is reached. Then the oldest trace file is overwritten. (For more information about how log files are created, see the JUNOS System Log Messages Reference.)
Log files can be accessed only by the user who configures the tracing operation.

You cannot change the directory (/var/log) in which trace files are located. However, you can customize the other trace file settings by including the following statements at the [edit snmp] hierarchy level:



[edit snmp]

traceoptions {
file filename  <files number> <size size> <world-readable
| no-world-readable> <match regex>;
flag flag;
}

These statements are described in the following sections:

Configuring the SNMP Log Filename

By default, the name of the file that records trace output is snmpd. You can specify a different name by including the file statement at the [edit snmp traceoptions] hierarchy level:



[edit snmp traceoptions]
file filename;

Configuring the Number and Size of SNMP Log Files

By default, when the trace file reaches 128 kilobytes (KB) in size, it is renamed filename.0, then filename.1, and so on, until there are three trace files. Then the oldest trace file (filename.2) is overwritten.

You can configure the limits on the number and size of trace files by including the following statements at the [edit snmp traceoptions] hierarchy level:



[edit snmp traceoptions]
file files number size size;

For example, set the maximum file size to 2 MB, and the maximum number of files to 20. When the file that receives the output of the tracing operation (filename) reaches 2 MB, filename is renamed filename.0, and a new file called filename is created. When the new filename reaches 2 MB, filename.0 is renamed filename.1 and filename is renamed filename.0. This process repeats until there are 20 trace files. Then the oldest file (filename.19) is overwritten by the newest file (filename.0).

The number of files can be from 2 through 1000 files. The file size of each file can be from 10 KB through 1 gigabyte (GB).

Configuring Access to the Log File

By default, log files can be accessed only by the user who configures the tracing operation.

To specify that any user can read all log files, include the file world-readable statement at the [edit snmp traceoptions] hierarchy level:



[edit snmp traceoptions]
file world-readable;

To explicitly set the default behavior, include the file no-world-readable statement at the [edit snmp traceoptions] hierarchy level:



[edit snmp traceoptions]
file no-world-readable;

Configuring a Regular Expression for Lines to Be Logged

By default, the trace operation output includes all lines relevant to the logged activities.

You can refine the output by including the match statement at the [edit snmp traceoptions file filename] hierarchy level and specifying a regular expression (regex) to be matched:



[edit snmp traceoptions]
file filename match regex;

Configuring the Trace Operations

By default, only important activities are logged. You can specify which trace operations are to be logged by including the following flag statement (with one or more tracing flags) at the [edit snmp traceoptions] hierarchy level:



[edit snmp traceoptions]
flag {
all;
configuration;
database;
events;
general;
interface-stats;
nonvolatile-sets;
pdu;
policy:
protocol-timeouts;
routing-socket;
server;
subagent;
timer;
varbind-error;
}

Table 9 describes the meaning of the SNMP tracing flags.

Table 9: SNMP Tracing Flags

Flag	Description	Default Setting
all	Log all operations.	Off
configuration	Log reading of configuration at the [edit snmp] hierarchy level.	Off
database	Log events involving storage and retrieval in events database.	Off
events	Log important events.	Off
general	Log general events.	Off
interface-stats	Log physical and logical interface statistics.	Off
nonvolatile-set	Log nonvolatile SNMP set request handling.	Off
pdu	Log SNMP request and response packets.	Off
policy	Log policy processing.	Off
protocol-timeouts	Log SNMP response timeouts.	Off
routing-socket	Log routing socket calls.	Off
server	Log communication with processes that are generating events.	Off
subagent	Log subagent restarts.	Off
timer	Log internal timer events.	Off
varbind-error	Log variable binding errors.	Off

To display the end of the log for an agent, issue the show log agentd | last operational mode command:



[edit]
user@host# run show log agentd | last

where agent is the name of an SNMP agent.

Example: Tracing SNMP Activity

Trace information about SNMP packets:



[edit]
snmp {


traceoptions {
file size 10k files 5;
flag pdu;
flag protocol-timeouts;
flag varbind-error;
}


}

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