SNMPTrap not reading snmp traffic through logstash

Elastic Stack Logstash
5

I am confused as to what you have configured.

This worked fine for me (I used the default 1062 port, rather than the privileged 162 - but should this should not matter)

Logstash config

input {
  snmptrap {}
}

filter {
}

output {
  stdout {
    codec => rubydebug { metadata => true }
  }
}

Test trap command

$ snmptrap -v 2c -c public localhost:1062 '' .1.3.6.1.6.3.1.1.5.3 ifIndex i 2 ifAdminStatus i 1 ifOperStatus i 1

Logstash stdout

logstash-2.3.2$ bin/logstash -f ../logstash-snmp.config
Settings: Default pipeline workers: 4
Pipeline main started
{
                      "message" => "#<SNMP::SNMPv2_Trap:0x37c613c @request_id=1803122945, @error_index=0, @error_status=0, @source_ip=\"127.0.0.1\", @varbind_list=[#<SNMP::VarBind:0x42416b07 @name=[1.3.6.1.2.1.1.3.0], @value=#<SNMP::TimeTicks:0x13dc79f2 @value=59480382>>, #<SNMP::VarBind:0x73c98f34 @name=[1.3.6.1.6.3.1.1.4.1.0], @value=[1.3.6.1.6.3.1.1.5.3]>, #<SNMP::VarBind:0x6bbec36b @name=[1.3.6.1.2.1.2.2.1.1], @value=#<SNMP::Integer:0x226e9448 @value=2>>, #<SNMP::VarBind:0x528d6a1e @name=[1.3.6.1.2.1.2.2.1.7], @value=#<SNMP::Integer:0x6d02ef54 @value=1>>, #<SNMP::VarBind:0x70bacc04 @name=[1.3.6.1.2.1.2.2.1.8], @value=#<SNMP::Integer:0x2620ca8f @value=1>>]>",
                         "host" => "127.0.0.1",
                     "@version" => "1",
                   "@timestamp" => "2016-07-25T16:03:32.834Z",
      "SNMPv2-MIB::sysUpTime.0" => "6 days, 21:13:23.82",
    "SNMPv2-MIB::snmpTrapOID.0" => "IF-MIB::linkDown",
              "IF-MIB::ifIndex" => "2",
        "IF-MIB::ifAdminStatus" => "1",
         "IF-MIB::ifOperStatus" => "1"
}

Maybe post the details of the trap from tcpdump?