Essential SNMP

Retrieving Multiple MIB Values

The syntax for snmpwalk is similar to the syntax for its cousin, snmpget. As discussed in Chapter 2, snmpwalk traverses a MIB starting with some object, continuously returning values until it gets to the end of that object’s branch. For example, the upcoming Perl script begins walking the .iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifDescr object and provides a description of each Ethernet interface on the device it polls.

This new script is a minor modification of snmpget.pl. We turned the scalar $value into the array @values;^[32] we need an array because we expect to get multiple values back. We also called the function snmpwalk instead of snmpget (syntactically, the two functions are the same):

#!/usr/local/bin/perl
#filename: /opt/local/perl_scripts/snmpwalk.pl
use SNMP_util;
$MIB1 = shift;
$HOST = shift;
($MIB1) && ($HOST) || die "Usage: $0 MIB_OID HOSTNAME";
(@values) = &snmpwalk("$HOST","$MIB1");
if (@values) { print "Results :$MIB1: :@values:\n"; }
else { warn "No response from host :$HOST:\n"; }

Here’s how to run the script:

$ /opt/local/perl_scripts/snmpwalk.pl .1.3.6.1.2.1.2.2.1.2 orarouter1

This command walks down the .iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifDescr object, returning information about the interfaces that are on the router. The results look something like this:

Results :.1.3.6.1.2.1.2.2.1.2: :1:Ethernet0 2:Serial0 3:Serial1:

The output depends on the interfaces on the host or router ...