snmp4j snmpwalk with Community String Indexing

Question

How to do a snmpwalk with snmp4j and Community String Indexing?

I can do a Community String Indexing by changing the community String like public@123 (123 is the vlanId)

But this works only with snmpget !!??:

public ResponseEvent get(OID oids) throws IOException {
    PDU pdu = new PDU();
    pdu.add(new VariableBinding(oid));
    pdu.setType(PDU.GETNEXT);
    ResponseEvent event = snmp.send(pdu, getTarget(), null);
}

private Target getTarget() {
    Address targetAddress = GenericAddress.parse(sw.getAddress());
    CommunityTarget target = new CommunityTarget();
    target.setCommunity(new OctetString(communityString));
    target.setAddress(targetAddress);
    target.setRetries(2);
    target.setTimeout(1500);
    target.setVersion(SnmpConstants.version2c);
    return target;
}

But when I try to do a snmpwalk like this i get a timeout

public HashMap<String, String> snmpWalk(String strOid) throws IOException {
    OID oid = new OID(strOid);
    TreeUtils treeUtils = new TreeUtils(snmp, new DefaultPDUFactory());
    HashMap<String, String> snmpResult = new HashMap<String, String>();
    List<TreeEvent> events = treeUtils.getSubtree(getTarget(), oid);
    // some more code ...
}

score 1 · Accepted Answer · answered Oct 17 '13 at 11:58

I fixed the problem by writing a SNMP-walk method using GETBULK

It is important to set the maxRepetitions and maxSizeResponsePDU I use this values:

/** maxRepetitions needs to be set for BULKGET to work<br>
 * it defines the maximum lines/results returned for one request. 
 */
private int maxRepetitions = 50;

/** maxSizeResponsePDU needs to be set for BULKGET to work */
private int maxSizeResponsePDU = 65535;

public HashMap<String, String> snmpWalk (String startOid) throws IOException{
    //String startOid = "1.3.6.1.4.1.9.9.46.1.3.1.1.4.1"; 
    String oid = startOid;
    HashMap<String, String> varBindings = new HashMap<String, String>();

    while (oid.startsWith(startOid)) {
        PDU pdu = getVariableBinding(new OID(oid), PDU.GETBULK);
        if (pdu == null || pdu.size() == 0) return varBindings;

        for (int i=0; i<pdu.size(); i++) {
            VariableBinding var = pdu.get(i);
            if (var == null) return varBindings;

            oid = var.getOid().toString();
            if (oid.startsWith(startOid)) {
                varBindings.put(oid, var.getVariable().toString());
            } else {
                return varBindings;
            }
        }
    }
    return varBindings;
}

/**
 * Method which takes a single OID and returns the response from the agent
 * as a String.
 * 
 * @param oid
 * @return
 * @throws IOException
 */
public PDU getVariableBinding(OID oid, int type) throws IOException {
    ResponseEvent event = get(new OID[] { oid }, type);

    if (event == null || event.getResponse() == null) {
        warn(oid);
        return null;
    }

    return event.getResponse();
}

public ResponseEvent get(OID oids[], int type) throws IOException {
    PDU pdu = new PDU();
    for (OID oid : oids) {
        pdu.add(new VariableBinding(oid));
    }
    pdu.setType(type);

    pdu.setMaxRepetitions(maxRepetitions); // This makes GETBULK work as expected

    ResponseEvent event = snmp.send(pdu, getTarget(), null);
    if (event != null) {
        return event;
    }
    throw new RuntimeException("GET timed out");
}

private Target getTarget() {
    Address targetAddress = GenericAddress.parse(sw.getAddress());
    CommunityTarget target = new CommunityTarget();
    target.setCommunity(new OctetString(communityString));
    target.setAddress(targetAddress);
    target.setRetries(2);
    target.setTimeout(3000);
    target.setVersion(SnmpConstants.version2c);

    target.setMaxSizeRequestPDU(maxSizeResponsePDU); // This makes GETBULK work as expected

    return target;
}

score 1 · Answer 2 · answered Feb 02 '14 at 10:25

1

With SNMP4J there is the TreeUtils class which provides already the "walk" functionality you implemented here and which sets reasonable defaults for the maxRepetitions and nonRepeaters fields.

answered Feb 02 '14 at 10:25

ooSNMP

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snmp4j snmpwalk with Community String Indexing

2 Answers2