# Packet beat Reverse DNS lookup not working properly

**URL:** <https://discuss.elastic.co/t/packet-beat-reverse-dns-lookup-not-working-properly/183285>\
**Category:** Beats\
**Created:** [May 29, 2019, 9:09am UTC](https://discuss.elastic.co/t/packet-beat-reverse-dns-lookup-not-working-properly/183285 "2019-05-29T09:09:15Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![swapnali](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@swapnali](https://discuss.elastic.co/u/swapnali)\
**Post date:** [May 29, 2019, 9:09am UTC](https://discuss.elastic.co/t/packet-beat-reverse-dns-lookup-not-working-properly/183285/1 "2019-05-29T09:09:15Z")

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Hi,

following are configuration of packetbeat for Reverse DNS lookup

processors:

- dns:  
type: reverse  
action: append  
fields:  
server.ip: server.hostname  
client.ip: client.hostname  
success\_cache:  
capacity.initial: 1000  
capacity.max: 10000  
failure\_cache:  
capacity.initial: 1000  
capacity.max: 10000  
ttl: 1m  
nameservers: ['ip\_addres']  
timeout: 500ms  
tag\_on\_failure: [\_dns\_reverse\_lookup\_failed]

But i have no clarity what should i mention in below field

server.ip: server.hostname  
client.ip: client.hostname

I have referring following document for same but its not giving clarity to me.  
[https://www.elastic.co/guide/en/beats/filebeat/master/processor-dns.html](https://www.elastic.co/guide/en/beats/filebeat/master/processor-dns.html)

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<div class="post-metadata">

**Author:** ![adrisr](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/adrisr/32/25423_2.png) [@adrisr](https://discuss.elastic.co/u/adrisr)\
**Post date:** [May 29, 2019, 12:34pm UTC](https://discuss.elastic.co/t/packet-beat-reverse-dns-lookup-not-working-properly/183285/2 "2019-05-29T12:34:07Z")

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Can you please format your configuration using the `</>` button so it's easier to tell how it is indented?

Which version of Packetbeat are you using?

> [@swapnali](#):
>
> But i have no clarity what should i mention in below field  
> fields:  
> server.ip: server.hostname  
> client.ip: client.hostname

The `dns` processor with `type: reverse` (currently the only supported type) will take a field whose value is an IP and perform a reverse DNS query to obtain the domain that resolves to that IP.

The `fields` mapping here will take each source IP field (`server.ip` and `client.ip` in this example) and resolve each IP storing the resulting domain in the mapped field (`server.hostname` and `client.hostname`, respectively).

When you say it doesn't work, do you mean that the hostname fields are not being created, or are you getting an error?

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<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:** [June 26, 2019, 2:34pm UTC](https://discuss.elastic.co/t/packet-beat-reverse-dns-lookup-not-working-properly/183285/3 "2019-06-26T14:34:15Z")

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