SNMP Operations Deep Dive

A comprehensive guide to all SNMP operations in SnmpKit.

Setup

Mix.install([
  {:snmpkit, "~> 1.3"}
])

alias SnmpKit.{SNMP, Sim}

Create Test Devices

We’ll create two simulated devices to demonstrate various operations.

# Cable modem with traffic counters
cable_modem_oids = %{
  "1.3.6.1.2.1.1.1.0" => "ARRIS SURFboard SB8200 DOCSIS 3.1 Cable Modem",
  "1.3.6.1.2.1.1.2.0" => "1.3.6.1.4.1.4115.1.20.1",
  "1.3.6.1.2.1.1.3.0" => %{type: "TimeTicks", value: 987654},
  "1.3.6.1.2.1.1.4.0" => "admin@example.com",
  "1.3.6.1.2.1.1.5.0" => "cm-001",
  "1.3.6.1.2.1.1.6.0" => "Home Network",
  "1.3.6.1.2.1.2.1.0" => 2,
  "1.3.6.1.2.1.2.2.1.1.1" => 1,
  "1.3.6.1.2.1.2.2.1.1.2" => 2,
  "1.3.6.1.2.1.2.2.1.2.1" => "cable-downstream0",
  "1.3.6.1.2.1.2.2.1.2.2" => "cable-upstream0",
  "1.3.6.1.2.1.2.2.1.3.1" => 127,
  "1.3.6.1.2.1.2.2.1.3.2" => 127,
  "1.3.6.1.2.1.2.2.1.10.1" => %{type: "Counter32", value: 1500000},
  "1.3.6.1.2.1.2.2.1.16.1" => %{type: "Counter32", value: 900000}
}

{:ok, cm_profile} = SnmpKit.SnmpSim.ProfileLoader.load_profile(:cable_modem, {:manual, cable_modem_oids})
{:ok, _cm} = Sim.start_device(cm_profile, port: 1161)

# Router with more interfaces
router_oids = %{
  "1.3.6.1.2.1.1.1.0" => "Cisco IOS Software, C2900 Software, Version 15.1(4)M12a",
  "1.3.6.1.2.1.1.2.0" => "1.3.6.1.4.1.9.1.576",
  "1.3.6.1.2.1.1.3.0" => %{type: "TimeTicks", value: 456789},
  "1.3.6.1.2.1.1.4.0" => "netops@company.com",
  "1.3.6.1.2.1.1.5.0" => "router-001",
  "1.3.6.1.2.1.1.6.0" => "Data Center",
  "1.3.6.1.2.1.2.1.0" => 4,
  "1.3.6.1.2.1.2.2.1.1.1" => 1,
  "1.3.6.1.2.1.2.2.1.1.2" => 2,
  "1.3.6.1.2.1.2.2.1.1.3" => 3,
  "1.3.6.1.2.1.2.2.1.1.4" => 4,
  "1.3.6.1.2.1.2.2.1.2.1" => "GigabitEthernet0/0",
  "1.3.6.1.2.1.2.2.1.2.2" => "GigabitEthernet0/1",
  "1.3.6.1.2.1.2.2.1.2.3" => "Serial0/0/0",
  "1.3.6.1.2.1.2.2.1.2.4" => "Loopback0",
  "1.3.6.1.2.1.2.2.1.5.1" => %{type: "Gauge32", value: 1000000000},
  "1.3.6.1.2.1.2.2.1.5.2" => %{type: "Gauge32", value: 1000000000},
  "1.3.6.1.2.1.2.2.1.5.3" => %{type: "Gauge32", value: 1544000},
  "1.3.6.1.2.1.2.2.1.8.1" => 1,
  "1.3.6.1.2.1.2.2.1.8.2" => 1,
  "1.3.6.1.2.1.2.2.1.8.3" => 2,
  "1.3.6.1.2.1.2.2.1.8.4" => 1
}

{:ok, router_profile} = SnmpKit.SnmpSim.ProfileLoader.load_profile(:router, {:manual, router_oids})
{:ok, _router} = Sim.start_device(router_profile, port: 1162)

cm_target = "127.0.0.1:1161"
router_target = "127.0.0.1:1162"

IO.puts("Devices ready:")
IO.puts("  Cable modem: #{cm_target}")
IO.puts("  Router: #{router_target}")

Basic GET Operations

Simple GET

cm_target = "127.0.0.1:1161"

# Get returns an enriched map with multiple fields
{:ok, result} = SNMP.get(cm_target, "sysDescr.0")

IO.puts("Enriched result:")
IO.puts("  OID: #{result.oid}")
IO.puts("  Type: #{result.type}")
IO.puts("  Raw value: #{inspect(result.value)}")
IO.puts("  Formatted: #{result.formatted}")
IO.puts("  Name: #{result.name}")

GET with Options

cm_target = "127.0.0.1:1161"

# Custom timeout and community
{:ok, result} = SNMP.get(cm_target, "sysUpTime.0",
  timeout: 5000,
  community: "public"
)

IO.puts("Uptime: #{result.formatted}")

GETNEXT

Get the next OID in the tree:

cm_target = "127.0.0.1:1161"

{:ok, result} = SNMP.get_next(cm_target, "sysDescr")
IO.puts("Next after sysDescr: #{result.oid} = #{result.formatted}")

{:ok, result2} = SNMP.get_next(cm_target, result.oid)
IO.puts("Next after that: #{result2.oid} = #{result2.formatted}")

WALK Operations

Basic Walk

cm_target = "127.0.0.1:1161"

{:ok, results} = SNMP.walk(cm_target, "system")

IO.puts("System group:")
Enum.each(results, fn %{oid: oid, type: type, formatted: value} ->
  IO.puts("  #{oid} (#{type}) = #{value}")
end)

Walk with Pretty Output

router_target = "127.0.0.1:1162"

{:ok, results} = SNMP.walk_pretty(router_target, "ifDescr")

IO.puts("Interface descriptions:")
Enum.each(results, fn %{oid: oid, formatted: value} ->
  IO.puts("  #{oid}: #{value}")
end)

Bulk Operations

Bulk operations are more efficient for retrieving large amounts of data.

GETBULK

router_target = "127.0.0.1:1162"

{:ok, results} = SNMP.get_bulk(router_target, "interfaces", max_repetitions: 10)

IO.puts("Bulk get returned #{length(results)} objects:")
Enum.take(results, 5) |> Enum.each(fn %{oid: oid, formatted: value} ->
  IO.puts("  #{oid} = #{value}")
end)

Bulk Walk

router_target = "127.0.0.1:1162"

{:ok, results} = SNMP.bulk_walk(router_target, "interfaces")

IO.puts("Bulk walk returned #{length(results)} objects")

Adaptive Walk

Automatically optimizes bulk parameters based on device response:

router_target = "127.0.0.1:1162"

{:ok, results} = SNMP.adaptive_walk(router_target, "interfaces")

IO.puts("Adaptive walk returned #{length(results)} objects")

Multi-Target Operations

Query multiple devices simultaneously.

GET Multiple Targets

cm_target = "127.0.0.1:1161"
router_target = "127.0.0.1:1162"

requests = [
  {cm_target, "sysDescr.0"},
  {router_target, "sysDescr.0"},
  {cm_target, "sysName.0"},
  {router_target, "sysName.0"}
]

results = SNMP.get_multi(requests)

IO.puts("Multi-target results:")
Enum.zip(requests, results)
|> Enum.each(fn {{target, oid}, result} ->
  case result do
    {:ok, [%{formatted: value} | _]} ->
      IO.puts("  #{target} #{oid}: #{value}")
    {:error, reason} ->
      IO.puts("  #{target} #{oid}: ERROR - #{inspect(reason)}")
  end
end)

WALK Multiple Targets

cm_target = "127.0.0.1:1161"
router_target = "127.0.0.1:1162"

walk_requests = [
  {cm_target, "system"},
  {router_target, "system"}
]

results = SNMP.walk_multi(walk_requests)

IO.puts("Multi-target walk:")
Enum.zip(walk_requests, results)
|> Enum.each(fn {{target, oid}, result} ->
  case result do
    {:ok, data} ->
      IO.puts("  #{target} #{oid}: #{length(data)} objects")
    {:error, reason} ->
      IO.puts("  #{target} #{oid}: ERROR - #{inspect(reason)}")
  end
end)

Streaming Operations

For very large tables, use streaming to process data without loading everything into memory.

router_target = "127.0.0.1:1162"

stream = SNMP.walk_stream(router_target, "interfaces")

IO.puts("Streaming interface data:")
stream
|> Stream.take(5)
|> Enum.each(fn %{oid: oid, type: type, formatted: value} ->
  IO.puts("  #{oid} (#{type}) = #{value}")
end)

Error Handling

# Timeout handling
case SNMP.get("192.168.255.255:161", "sysDescr.0", timeout: 1000) do
  {:ok, result} -> IO.puts("Got: #{result.formatted}")
  {:error, :timeout} -> IO.puts("Request timed out")
  {:error, reason} -> IO.puts("Error: #{inspect(reason)}")
end

Next Steps

• MIB Management - OID resolution and custom MIBs
• Device Simulation - Build realistic test devices
• High Performance - Scale to thousands of devices