gsub issue - example data

gistfile1.txt

{
  "_index": "logstash-2014.11.17",
  "_type": "netflow",
  "_id": "tN86DepHQ5yOaetLMVDRCA",
  "_score": null,
  "_source": {
    "@timestamp": "2014-11-17T21:33:03.000Z",
    "netflow": {
      "version": "9",
      "flow_seq_num": "254",
      "flowset_id": "257",
      "in_bytes": "152",
      "in_pkts": "1",
      "protocol": "6",
      "src_tos": "0",
      "tcp_flags": "24",
      "l4_src_port": "8080",
      "ipv4_src_addr": "10.25.200.107",
      "src_mask": "0",
      "input_snmp": "0",
      "l4_dst_port": "60558",
      "ipv4_dst_addr": "10.25.14.116",
      "dst_mask": "0",
      "output_snmp": "0",
      "ipv4_next_hop": "0.0.0.0",
      "src_as": "0",
      "dst_as": "0",
      "last_switched": "2014-11-17T21:33:03.999Z",
      "first_switched": "2014-11-17T21:33:03.999Z"
    },
    "@version": "1",
    "type": "netflow",
    "tags": [
      "nProbe",
      "netflow_if_statement_hit"
    ],
    "host": "TCP"
  },
  "sort": [
    1416259983000,
    1416259983000
  ]
}