# Logstash DNS Filter Issue

**URL:** <https://discuss.elastic.co/t/logstash-dns-filter-issue/123818>\
**Category:** Logstash\
**Created:** [March 13, 2018, 10:43pm UTC](https://discuss.elastic.co/t/logstash-dns-filter-issue/123818 "2018-03-13T22:43:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sysadmin007](https://avatars.discourse-cdn.com/v4/letter/s/4bbf92/32.png) [@sysadmin007](https://discuss.elastic.co/u/sysadmin007)\
**Post date:** [March 13, 2018, 10:43pm UTC](https://discuss.elastic.co/t/logstash-dns-filter-issue/123818/1 "2018-03-13T22:43:55Z")

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Hello All,  
I setup an ELK Stack with the latest version of logstash 6.2.2 on Ubuntu 17.10. The setup went ok i have netflow records in my Kibana dashboard and most everything seems to be working properly. The only issue I am stumped on is making the DNS filter work to resolve 1 field in my netflow data. It seems the fields from mutate just never appear anywhere in Kibana. Any help would be greatly appreciated as I have been working on this the last week trying so many solutions. Thank you!

netflow.conf in /etc/logstash/conf.d directory

```
input {
    udp {
        port => 9991
        codec => netflow
    }
}
 filter {
         mutate {
                add_field => { "dst_host" => "%{[netflow][dst_addr]}" }
      }
         dns {
                # DNS Filter
                reverse => ["dst_host"]
                action => "replace"
                nameserver => ["10.0.100.8"]
                hit_cache_size => 4096
                hit_cache_ttl => 900
                failed_cache_size => 512
                failed_cache_ttl => 900
       }

}
output {
    elasticsearch {
        hosts => ["localhost:9200"]
    }
}

```

logstash.yml

```
 modules:
      - name: netflow
        var.input.udp.port: 9991
```

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 10, 2018, 10:43pm UTC](https://discuss.elastic.co/t/logstash-dns-filter-issue/123818/2 "2018-04-10T22:43:59Z")

</div>

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