snmpwalk
(PHP 4, PHP 5)
snmpwalk — Fetch all the SNMP objects from an agent
Описание
snmpwalk() function is used to read all the values from an SNMP agent specified by the hostname .
Список параметров
- hostname
-
The SNMP agent.
- community
-
The read community.
- object_id
-
If NULL, object_id is taken as the root of the SNMP objects tree and all objects under that tree are returned as an array.
If object_id is specified, all the SNMP objects below that object_id are returned.
- timeout
-
- retries
-
Возвращаемые значения
Returns an array of SNMP object values starting from the object_id as root or FALSE on error.
Примеры
Пример #1 snmpwalk() Example
<?php
$a = snmpwalk("127.0.0.1", "public", "");
foreach ($a as $val) {
echo "$val\n";
}
?>
Above function call would return all the SNMP objects from the SNMP agent running on localhost. One can step through the values with a loop
- snmp_get_quick_print
- snmp_get_valueretrieval
- snmp_read_mib
- snmp_set_enum_print
- snmp_set_oid_numeric_print
- snmp_set_oid_output_format
- snmp_set_quick_print
- snmp_set_valueretrieval
- snmp2_get
- snmp2_getnext
- snmp2_real_walk
- snmp2_set
- snmp2_walk
- snmp3_get
- snmp3_getnext
- snmp3_real_walk
- snmp3_set
- snmp3_walk
- snmpget
- snmpgetnext
- snmprealwalk
- snmpset
- snmpwalk
- snmpwalkoid
Коментарии
A quick router device view:
<?
include "header.html";
$host = "auscr1";
$community = "tellme";
$sysDescr = snmpget("$host","$community","system.sysDescr.0");
$ifDescr = snmpwalk("$host","$community","interfaces.ifTable.ifEntry.ifDescr");
$ifIndex = snmpwalk("$host","$community","interfaces.ifTable.ifEntry.ifIndex");
$ifAdminStatus = snmpwalk("$host","$community","interfaces.ifTable.ifEntry.ifAdminStatus");
$ifOperStatus = snmpwalk("$host","$community","interfaces.ifTable.ifEntry.ifOperStatus");
$ifLastChange = snmpwalk("$host","$community","interfaces.ifTable.ifEntry.ifLastChange");
print "<table border=1 bgcolor=#ffffff><tr><td>$host</td></tr></table><br>";
print "<table border=1 bgcolor=#ffffff><tr><td>$sysDescr</td></tr></table><br>";
print "<table border=1 bgcolor=#ffffff>";
print "<tr>
<td>ifIndex</td>
<td>ifDescr</td>
<td>ifAdminStatus</td>
<td>ifOperStatus</td>
<td>ifLastChange</td>
</tr>";
for ($i=0; $i<count($ifIndex); $i++) {
print "<tr>";
print "<td>$ifIndex[$i]</td>";
print "<td>$ifDescr[$i]</td>";
print "<td>$ifAdminStatus[$i]</td>";
print "<td>$ifOperStatus[$i]</td>";
print "<td>$ifLastChange[$i]</td>";
print "</tr>";
}
print "</table>";
?>
for the poster wondering what the
timeout field was measured in:
from the ucd-snmp header file snmp_api.h:
long timeout;
/* Number of uS until first timeout
then exponential backoff */
Ah. That's why all of our SNMP stuff was timing out anytime there was any load on the system. Sigh. A waste of two weeks trying to debug snmp....
Even the snmpcmd manpage doesn't give a
unit for timeout.
Something to care about in dealing with snmpwalk:<BR>While walking the MIB, snmpwalk puts info that gets into an array, and that is correct.<BR>
The trouble happened when snmpwalk needs to collect information from instances that contains subinstances (i.e. walking .1.2.3.4.5 and having instances like 1.1, 1.2, 1.3): in this case it gets info and passes into an array, but when walking the array, each value is preceeded by 'Counter32: '.<BR>
I've tested this in many ways and it always happened the same way.
Timeout is in MICRO seconds.1,000,000 µs = 1 s
It would be nice to be able to specify what snmp version to use ( 1,2c,3 )
For now, I'ts hardcoded in ext/snmp/snmp.c
change session.version from 1 to 2c or 3 if you need for now..
i.e
session.version = SNMP_VERSION_1;
to:
session.version = SNMP_VERSION_2c;
Note that there's different behaviuor in php snmpwalk and ucd snmpwalk. If you try to walk an oid that has one value not under a subkey of the walked oid, ucd snmpwalk will return the value while php's snmpwalk will not.I had to use an object_id like these.
'SNMPv2-MIB::system.sysDescr.0'
'IF-MIB::interfaces.ifTable.ifEntry.ifAdminStatus'
<?php
$host = '192.168.1.1';
$community = 'public';
$object_id = 'IF-MIB::interfaces.ifTables.ifEntry.ifAdminStatus';
$sysdesc = snmpwalk($host, $community', $object_id);
print_r($sysdesc);
?>
I found on Windows (PHP 5) an empty string did not return anything, it just timed out. I had to use null instead:
<?php
$a = snmpwalk("127.0.0.1", "public", null);
?>
snmpwalk and other snmp functions really need to support an optional port.
In the corporate world it is very common to change the port for SNMP from 161 to some other port for security. It is a simple security obfuscation, but a lot of bots will scan well known ports for attack vectors. For example, we used to change ours to something like 1161 just to prevent making it easy.