# Various SNMP versions

## Multiple SNMP USM users

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

- SNMPv3

- with USM user ‘usr-md5-des’, auth: MD5, priv DES or with USM user ‘usr-sha-none’, auth: SHA, no privacy with USM user ‘usr-sha-aes128’, auth: SHA, priv AES

- allow access to SNMPv2-MIB objects (1.3.6.1.2.1)

- over IPv4/UDP, listening at 127.0.0.1:161

Either of the following Net-SNMP commands will walk this Agent:

$ snmpwalk -v3 -u usr-md5-des -l authPriv -A authkey1 -X privkey1 localhost .1.3.6
$ snmpwalk -v3 -u usr-sha-none -l authNoPriv -a SHA -A authkey1 localhost .1.3.6
$ snmpwalk -v3 -u usr-sha-aes128 -l authPriv -a SHA -A authkey1 -x AES -X privkey1 localhost .1.3.6

    from pysnmp.entity import engine, config
    from pysnmp.entity.rfc3413 import cmdrsp, context
    from pysnmp.carrier.asyncore.dgram import udp

    # Create SNMP engine
    snmpEngine = engine.SnmpEngine()

    # Transport setup

    # UDP over IPv4
    config.addTransport(
        snmpEngine,
        udp.domainName,
        udp.UdpTransport().openServerMode(('127.0.0.1', 1161))
    )

    # SNMPv3/USM setup

    # user: usr-md5-des, auth: MD5, priv DES
    config.addV3User(
        snmpEngine, 'usr-md5-des',
        config.usmHMACMD5AuthProtocol, 'authkey1',
        config.usmDESPrivProtocol, 'privkey1'
    )
    # user: usr-sha-none, auth: SHA, priv NONE
    config.addV3User(
        snmpEngine, 'usr-sha-none',
        config.usmHMACSHAAuthProtocol, 'authkey1'
    )
    # user: usr-sha-none, auth: SHA, priv AES
    config.addV3User(
        snmpEngine, 'usr-sha-aes128',
        config.usmHMACSHAAuthProtocol, 'authkey1',
        config.usmAesCfb128Protocol, 'privkey1'
    )

    # Allow full MIB access for each user at VACM
    config.addVacmUser(snmpEngine, 3, 'usr-md5-des', 'authPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))
    config.addVacmUser(snmpEngine, 3, 'usr-sha-none', 'authNoPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))
    config.addVacmUser(snmpEngine, 3, 'usr-sha-aes128', 'authPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))

    # Get default SNMP context this SNMP engine serves
    snmpContext = context.SnmpContext(snmpEngine)

    # Register SNMP Applications at the SNMP engine for particular SNMP context
    cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
    cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
    cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
    cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

    # Register an imaginary never-ending job to keep I/O dispatcher running forever
    snmpEngine.transportDispatcher.jobStarted(1)

    # Run I/O dispatcher which would receive queries and send responses
    try:
        snmpEngine.transportDispatcher.runDispatcher()
    except:
        snmpEngine.transportDispatcher.closeDispatcher()
        raise

`Download` script.

## Multiple SNMP communities

Respond to SNMP GET/SET/GETNEXT queries with the following options:

- SNMPv1

- with SNMP community “public” (read access) or “private” (write access)

- allow access to SNMPv2-MIB objects (1.3.6.1.2.1)

- over IPv4/UDP, listening at 127.0.0.1:161

Allow read/write access to all objects in the same MIB subtree.

The following Net-SNMP’s commands will GET/SET a value at this Agent:

$ snmpget -v1 -c public 127.0.0.1 SNMPv2-MIB::sysLocation.0
$ snmpset -v1 -c private 127.0.0.1 SNMPv2-MIB::sysLocation.0 s “far away”

    from pysnmp.entity import engine, config
    from pysnmp.entity.rfc3413 import cmdrsp, context
    from pysnmp.carrier.asyncore.dgram import udp

    # Create SNMP engine with autogenernated engineID and pre-bound
    # to socket transport dispatcher
    snmpEngine = engine.SnmpEngine()

    # Transport setup

    # UDP over IPv4
    config.addTransport(
        snmpEngine,
        udp.domainName,
        udp.UdpTransport().openServerMode(('127.0.0.1', 161))
    )

    # SNMPv1 setup

    # SecurityName <-> CommunityName mapping.
    # Here we configure two distinct CommunityName's to control read and write
    # operations.
    config.addV1System(snmpEngine, 'my-read-area', 'public')
    config.addV1System(snmpEngine, 'my-write-area', 'private')

    # Allow full MIB access for this user / securityModels at VACM
    config.addVacmUser(snmpEngine, 1, 'my-read-area', 'noAuthNoPriv', (1, 3, 6, 1, 2, 1))
    config.addVacmUser(snmpEngine, 1, 'my-write-area', 'noAuthNoPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))

    # Get default SNMP context this SNMP engine serves
    snmpContext = context.SnmpContext(snmpEngine)

    # Register SNMP Applications at the SNMP engine for particular SNMP context
    cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
    cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
    cmdrsp.NextCommandResponder(snmpEngine, snmpContext)

    # Register an imaginary never-ending job to keep I/O dispatcher running forever
    snmpEngine.transportDispatcher.jobStarted(1)

    # Run I/O dispatcher which would receive queries and send responses
    try:
        snmpEngine.transportDispatcher.runDispatcher()
    except:
        snmpEngine.transportDispatcher.closeDispatcher()
        raise

`Download` script.

See also: library reference.