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Example SNMP Walk Operation
qingxiao_ren edited this page Sep 5, 2018
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"Walk" is not a strictly speaking an SNMP operation. When you talk about "walking the MIB" you are talking about sequentially retrieving values from the MIB. To sequentially retrieve MIB values, you can use:
- GET-NEXT requests in protocol versions 1, 2 or 3
"Walk" is not a strictly speaking an SNMP operation. When you talk about "walking the MIB" you are talking about sequentially retrieving values from the MIB. To sequentially retrieve MIB values, you can use:
* GET-NEXT requests in protocol versions 1, 2 or 3
takes an OID and returns the OID following the requested MIB with the value associated with it
* GET-BULK requests in protocol versions 2 and 3
also takes an OID and then returns MaxRepetitions number of MIB entries following the requested OID
If you have any choice at all, you should always use GET-BULK. It results in fewer requests and much better retrieval speed.
using System;
using System.Net;
using SnmpSharpNet;
namespace sharpwalk
{
class Program
{
static void Main(string[] args)
{
// SNMP community name
OctetString community = new OctetString("public");
// Define agent parameters class
AgentParameters param = new AgentParameters(community);
// Set SNMP version to 1
param.Version = SnmpVersion.Ver1;
// Construct the agent address object
// IpAddress class is easy to use here because
// it will try to resolve constructor parameter if it doesn't
// parse to an IP address
IpAddress agent = new IpAddress("127.0.0.1");
// Construct target
UdpTarget target = new UdpTarget((IPAddress)agent, 161, 2000, 1);
// Define Oid that is the root of the MIB
// tree you wish to retrieve
Oid rootOid = new Oid("1.3.6.1.2.1.2.2.1.2"); // ifDescr
// This Oid represents last Oid returned by
// the SNMP agent
Oid lastOid = (Oid)rootOid.Clone();
// Pdu class used for all requests
Pdu pdu = new Pdu(PduType.GetNext);
// Loop through results
while (lastOid != null)
{
// When Pdu class is first constructed, RequestId is set to a random value
// that needs to be incremented on subsequent requests made using the
// same instance of the Pdu class.
if (pdu.RequestId != 0)
{
pdu.RequestId += 1;
}
// Clear Oids from the Pdu class.
pdu.VbList.Clear();
// Initialize request PDU with the last retrieved Oid
pdu.VbList.Add(lastOid);
// Make SNMP request
SnmpV1Packet result = (SnmpV1Packet)target.Request(pdu, param);
// You should catch exceptions in the Request if using in real application.
// If result is null then agent didn't reply or we couldn't parse the reply.
if (result != null)
{
// ErrorStatus other then 0 is an error returned by
// the Agent - see SnmpConstants for error definitions
if (result.Pdu.ErrorStatus != 0)
{
// agent reported an error with the request
Console.WriteLine("Error in SNMP reply. Error {0} index {1}",
result.Pdu.ErrorStatus,
result.Pdu.ErrorIndex);
lastOid = null;
break;
}
else
{
// Walk through returned variable bindings
foreach (Vb v in result.Pdu.VbList)
{
// Check that retrieved Oid is "child" of the root OID
if (rootOid.IsRootOf(v.Oid))
{
Console.WriteLine("{0} ({1}): {2}",
v.Oid.ToString(),
SnmpConstants.GetTypeName(v.Value.Type),
v.Value.ToString());
lastOid = v.Oid;
}
else
{
// we have reached the end of the requested
// MIB tree. Set lastOid to null and exit loop
lastOid = null;
}
}
}
}
else
{
Console.WriteLine("No response received from SNMP agent.");
}
}
target.Close();
}
}
}
using System;
using System.Net;
using SnmpSharpNet;
namespace sharpwalk
{
class Program
{
static void Main(string[] args)
{
// SNMP community name
OctetString community = new OctetString("public");
// Define agent parameters class
AgentParameters param = new AgentParameters(community);
// Set SNMP version to 2 (GET-BULK only works with SNMP ver 2 and 3)
param.Version = SnmpVersion.Ver2;
// Construct the agent address object
// IpAddress class is easy to use here because
// it will try to resolve constructor parameter if it doesn't
// parse to an IP address
IpAddress agent = new IpAddress("127.0.0.1");
// Construct target
UdpTarget target = new UdpTarget((IPAddress)agent, 161, 2000, 1);
// Define Oid that is the root of the MIB
// tree you wish to retrieve
Oid rootOid = new Oid("1.3.6.1.2.1.2.2.1.2"); // ifDescr
// This Oid represents last Oid returned by
// the SNMP agent
Oid lastOid = (Oid)rootOid.Clone();
// Pdu class used for all requests
Pdu pdu = new Pdu(PduType.GetBulk);
// In this example, set NonRepeaters value to 0
pdu.NonRepeaters = 0;
// MaxRepetitions tells the agent how many Oid/Value pairs to return
// in the response.
pdu.MaxRepetitions = 5;
// Loop through results
while (lastOid != null)
{
// When Pdu class is first constructed, RequestId is set to 0
// and during encoding id will be set to the random value
// for subsequent requests, id will be set to a value that
// needs to be incremented to have unique request ids for each
// packet
if (pdu.RequestId != 0)
{
pdu.RequestId += 1;
}
// Clear Oids from the Pdu class.
pdu.VbList.Clear();
// Initialize request PDU with the last retrieved Oid
pdu.VbList.Add(lastOid);
// Make SNMP request
SnmpV2Packet result = (SnmpV2Packet)target.Request(pdu, param);
// You should catch exceptions in the Request if using in real application.
// If result is null then agent didn't reply or we couldn't parse the reply.
if (result != null)
{
// ErrorStatus other then 0 is an error returned by
// the Agent - see SnmpConstants for error definitions
if (result.Pdu.ErrorStatus != 0)
{
// agent reported an error with the request
Console.WriteLine("Error in SNMP reply. Error {0} index {1}",
result.Pdu.ErrorStatus,
result.Pdu.ErrorIndex);
lastOid = null;
break;
}
else
{
// Walk through returned variable bindings
foreach (Vb v in result.Pdu.VbList)
{
// Check that retrieved Oid is "child" of the root OID
if (rootOid.IsRootOf(v.Oid))
{
Console.WriteLine("{0} ({1}): {2}",
v.Oid.ToString(),
SnmpConstants.GetTypeName(v.Value.Type),
v.Value.ToString());
if (v.Value.Type == SnmpConstants.SMI_ENDOFMIBVIEW)
lastOid = null;
else
lastOid = v.Oid;
}
else
{
// we have reached the end of the requested
// MIB tree. Set lastOid to null and exit loop
lastOid = null;
}
}
}
}
else
{
Console.WriteLine("No response received from SNMP agent.");
}
}
target.Close();
}
}
}
When I run either of the above examples on my notebook, I get following output:
1.3.6.1.2.1.2.2.1.2.1 (OctetString): Software Loopback Interface 1
1.3.6.1.2.1.2.2.1.2.2 (OctetString): WAN Miniport (L2TP)
1.3.6.1.2.1.2.2.1.2.3 (OctetString): WAN Miniport (PPTP)
1.3.6.1.2.1.2.2.1.2.4 (OctetString): WAN Miniport (PPPOE)
1.3.6.1.2.1.2.2.1.2.5 (OctetString): WAN Miniport (IPv6)
1.3.6.1.2.1.2.2.1.2.6 (OctetString): WAN Miniport (IP)
1.3.6.1.2.1.2.2.1.2.7 (OctetString): RAS Async Adapter
1.3.6.1.2.1.2.2.1.2.8 (OctetString): WAN Miniport (SSTP)
1.3.6.1.2.1.2.2.1.2.9 (OctetString): WAN Miniport (Network Monitor)
1.3.6.1.2.1.2.2.1.2.10 (OctetString): Realtek RTL8101E Family PCI-E FE NIC
1.3.6.1.2.1.2.2.1.2.11 (OctetString): Intel(R) PRO/Wireless 3945ABG Network Connection
1.3.6.1.2.1.2.2.1.2.12 (OctetString): Teredo Tunneling Pseudo-Interface
1.3.6.1.2.1.2.2.1.2.13 (OctetString): VMware Virtual Ethernet Adapter for VMnet1
1.3.6.1.2.1.2.2.1.2.14 (OctetString): isatap.{5D34A036-E8DD-4344-9CE3-58B461D1CB2A}
1.3.6.1.2.1.2.2.1.2.15 (OctetString): VMware Virtual Ethernet Adapter for VMnet8
1.3.6.1.2.1.2.2.1.2.16 (OctetString): isatap.{9195335D-923C-42BB-AC88-F54BC4501539}
1.3.6.1.2.1.2.2.1.2.17 (OctetString): isatap.hsd1.il.comcast.net.
1.3.6.1.2.1.2.2.1.2.18 (OctetString): Microsoft 6to4 Adapter
1.3.6.1.2.1.2.2.1.2.19 (OctetString): Microsoft ISATAP Adapter
1.3.6.1.2.1.2.2.1.2.20 (OctetString): WAN Miniport (IPv6)-QoS Packet Scheduler-0000
1.3.6.1.2.1.2.2.1.2.21 (OctetString): WAN Miniport (IP)-QoS Packet Scheduler-0000
1.3.6.1.2.1.2.2.1.2.22 (OctetString): WAN Miniport (Network Monitor)-QoS Packet Scheduler-0000
1.3.6.1.2.1.2.2.1.2.23 (OctetString): Realtek RTL8101E Family PCI-E FE NIC-QoS Packet Scheduler-0000
1.3.6.1.2.1.2.2.1.2.24 (OctetString): Intel(R) PRO/Wireless 3945ABG Network Connection-QoS [..]
1.3.6.1.2.1.2.2.1.2.25 (OctetString): Intel(R) PRO/Wireless 3945ABG Network Connection-Native [...]