net-snmp behavior changed in RHEL 5.7

Issue

In some older SNMP versions (like 5.3.2.2-9.el5_5.1) SNMP behaves differently then in newer versions (like 5.3.2.2-17.el5_8.1).
In these older versions we used to retrieve the indexes as follows:

oldVersion# snmpwalk -v2c -c public 127.0.0.1:161 -Of hrStorageDesc
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.1 = STRING: Memory Buffers
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.2 = STRING: Real Memory
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.3 = STRING: Swap Space
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.4 = STRING: /

and than use them to retrieve details about the specific disk device:

snmpget -v2c -c public 127.0.0.1:161 -On dskPercent.<instance>

But in newer net-snmp releases we get non-contiguous indexes:

newVersion# snmpwalk -v2c -c public 127.0.0.1:161 -Of hrStorageDesc
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.1 = STRING: Physical memory
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.3 = STRING: Virtual memory
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.6 = STRING: Memory buffers
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.7 = STRING: Cached memory
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.10 = STRING: Swap space
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.31 = STRING: /
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.35 = STRING: /tmp
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.36 = STRING: /opt
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.37 = STRING: /usr
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.38 = STRING: /var
.iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr.39 = STRING: /boot

but using them to retrive disk details with snmpget doesn't always work:

snmpget -v2c -c public 127.0.0.1:161 -On dskPercent.38