MIB Management

Understanding and working with MIBs (Management Information Bases) in SnmpKit.

Setup

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

alias SnmpKit.MIB

IO.puts("MIB module ready!")

What is a MIB?

A MIB defines the structure and meaning of SNMP data:

• Maps human-readable names to numeric OIDs
• Defines data types for each object
• Organizes objects into a hierarchical tree

SnmpKit includes standard MIBs (SNMPv2-MIB, IF-MIB, etc.) loaded by default.

OID Name Resolution

Resolve Names to OIDs

# Common SNMP objects
names = ["sysDescr", "sysUpTime", "sysContact", "sysName", "sysLocation", "ifNumber"]

IO.puts("Name to OID resolution:")
Enum.each(names, fn name ->
  case MIB.resolve(name) do
    {:ok, oid} ->
      IO.puts("  #{name} -> #{Enum.join(oid, ".")}")
    {:error, reason} ->
      IO.puts("  #{name} -> Error: #{inspect(reason)}")
  end
end)

Resolve with Instance Index

# Add .0 for scalar objects or .index for table entries
names_with_index = ["sysDescr.0", "sysUpTime.0", "ifDescr.1", "ifDescr.2"]

IO.puts("Names with instance index:")
Enum.each(names_with_index, fn name ->
  case MIB.resolve(name) do
    {:ok, oid} ->
      IO.puts("  #{name} -> #{Enum.join(oid, ".")}")
    {:error, _} ->
      IO.puts("  #{name} -> Not found")
  end
end)

Reverse Lookup

Convert OIDs back to names:

oids = [
  [1, 3, 6, 1, 2, 1, 1, 1, 0],      # sysDescr.0
  [1, 3, 6, 1, 2, 1, 1, 3, 0],      # sysUpTime.0
  [1, 3, 6, 1, 2, 1, 2, 1, 0],      # ifNumber.0
  [1, 3, 6, 1, 2, 1, 2, 2, 1, 2, 1] # ifDescr.1
]

IO.puts("OID to name resolution:")
Enum.each(oids, fn oid ->
  oid_str = Enum.join(oid, ".")
  case MIB.reverse_lookup(oid) do
    {:ok, name} ->
      IO.puts("  #{oid_str} -> #{name}")
    {:error, reason} ->
      IO.puts("  #{oid_str} -> #{inspect(reason)}")
  end
end)

Reverse Lookup from String

# Also works with string format
{:ok, name} = MIB.reverse_lookup("1.3.6.1.2.1.1.1.0")
IO.puts("1.3.6.1.2.1.1.1.0 -> #{name}")

MIB Tree Navigation

Get Children of a Node

# Get children of the system group
{:ok, system_oid} = MIB.resolve("system")
{:ok, children} = MIB.children(system_oid)

IO.puts("Children of 'system' (#{Enum.join(system_oid, ".")}):")
Enum.each(children, fn child_name ->
  case MIB.resolve(child_name) do
    {:ok, oid} ->
      IO.puts("  #{child_name} (#{Enum.join(oid, ".")})")
    {:error, _} ->
      IO.puts("  #{child_name}")
  end
end)

Get Parent of a Node

{:ok, sys_descr_oid} = MIB.resolve("sysDescr.0")
{:ok, parent_oid} = MIB.parent(sys_descr_oid)
{:ok, parent_name} = MIB.reverse_lookup(parent_oid)

IO.puts("sysDescr.0 parent: #{parent_name} (#{Enum.join(parent_oid, ".")})")

# Go up another level
{:ok, grandparent_oid} = MIB.parent(parent_oid)
{:ok, grandparent_name} = MIB.reverse_lookup(grandparent_oid)

IO.puts("sysDescr parent: #{grandparent_name} (#{Enum.join(grandparent_oid, ".")})")

Walk the MIB Tree

{:ok, mib_oid} = MIB.resolve("mib-2")
{:ok, tree} = MIB.walk_tree(mib_oid)

IO.puts("MIB-2 subtree (first 10 entries):")
tree
|> Enum.take(10)
|> Enum.each(fn {name, oid} ->
  IO.puts("  #{name}: #{Enum.join(oid, ".")}")
end)

Standard MIB Groups

SnmpKit includes these standard MIBs:

Note: The deprecated AT group (1.3.6.1.2.1.3) and ICMP group are not included.

groups = ["system", "interfaces", "ip", "tcp", "udp", "snmp"]

IO.puts("Standard MIB groups:")
Enum.each(groups, fn group ->
  case MIB.resolve(group) do
    {:ok, oid} ->
      {:ok, children} = MIB.children(oid)
      IO.puts("  #{group} (#{Enum.join(oid, ".")}): #{length(children)} children")
    {:error, _} ->
      IO.puts("  #{group}: Not found")
  end
end)

Common Interface Table OIDs

if_oids = [
  {"ifIndex", "Interface index"},
  {"ifDescr", "Interface description"},
  {"ifType", "Interface type"},
  {"ifMtu", "Maximum transmission unit"},
  {"ifSpeed", "Interface speed (bps)"},
  {"ifPhysAddress", "MAC address"},
  {"ifAdminStatus", "Admin status (up/down)"},
  {"ifOperStatus", "Operational status"},
  {"ifInOctets", "Bytes received"},
  {"ifOutOctets", "Bytes sent"}
]

IO.puts("Interface table columns:")
Enum.each(if_oids, fn {name, desc} ->
  case MIB.resolve(name) do
    {:ok, oid} ->
      IO.puts("  #{name}: #{Enum.join(oid, ".")} - #{desc}")
    {:error, _} ->
      IO.puts("  #{name}: Not in standard MIBs")
  end
end)

Enhanced Resolution

Get additional metadata about an OID:

case MIB.resolve_enhanced("sysDescr") do
  {:ok, info} ->
    IO.puts("Enhanced info for sysDescr:")
    IO.inspect(info, label: "  ")
  {:error, reason} ->
    IO.puts("Error: #{inspect(reason)}")
end

Using MIB Resolution with SNMP Operations

# Start a quick test device
device_oids = %{
  "1.3.6.1.2.1.1.1.0" => "Test Device",
  "1.3.6.1.2.1.1.5.0" => "test-device-01"
}

{:ok, profile} = SnmpKit.SnmpSim.ProfileLoader.load_profile(:test, {:manual, device_oids})
{:ok, _device} = SnmpKit.Sim.start_device(profile, port: 1163)

target = "127.0.0.1:1163"

# Use names instead of numeric OIDs
{:ok, result} = SnmpKit.SNMP.get(target, "sysDescr.0")
IO.puts("sysDescr.0: #{result.formatted}")

# The result includes the resolved name
IO.puts("Name in result: #{result.name}")

Next Steps

• Device Simulation - Create custom device profiles
• High Performance - Polling at scale