# DNS errors and Could not check for JavaScript support in docker instance

**URL:** <https://help.nextcloud.com/t/dns-errors-and-could-not-check-for-javascript-support-in-docker-instance/188438>\
**Category:** 📦 Appliances (Docker, Snappy, VM, NCP, AIO)\
**Tags:** reverseproxy, traefik, nc28, mjs\
**Created:** [April 18, 2024, 11:11am UTC](https://help.nextcloud.com/t/dns-errors-and-could-not-check-for-javascript-support-in-docker-instance/188438 "2024-04-18T11:11:53Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![wwe](https://help.nextcloud.com/user_avatar/help.nextcloud.com/wwe/32/72963_2.png) [@wwe](https://help.nextcloud.com/u/wwe)\
**Post date:** [April 18, 2024, 8:38pm UTC](https://help.nextcloud.com/t/dns-errors-and-could-not-check-for-javascript-support-in-docker-instance/188438/2 "2024-04-18T20:38:59Z")

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hi @Apfelwurm welcome back in the forum 🤝

> [@Apfelwurm](#):
>
> it resolves the public ipv4 and ipv6 without any problems.

Docker doesn’t play well with IPv6 _by default_.. this should not be a problem but more and more client prefer IPv6 and this could result in strange issues. maybe you start with IPv4-only and enable IPv6 once you know the system runs bullet-proof

Look at this topics - there are some hints regarding IPv6

- [Apache Docker behind reverse proxy](https://help.nextcloud.com/t/apache-docker-behind-reverse-proxy/151754)

> [@Probably DNS help with NC Docker + Collabora + Wireguard tunnel](https://help.nextcloud.com/t/probably-dns-help-with-nc-docker-collabora-wireguard-tunnel/176562/5):
>
> Docker IPv6 enabled /etc/docker/daemon.json
> 
> (majority of #docker installations will run using IPv4-only - which is default - and only require the 172.16.0.0/12 network)
> 
> ```auto
> {
> "userland-proxy": false,
> "ipv6": true,
> "fixed-cidr-v6": "fd00:beef:beef::/48",
> "experimental": true,
> "ip6tables": true
> }
> 
> ```

regarding the #mjs issue - I can not remember anybody reporting this issue with #traefik. I know it doesn’t really help to say “it works on my machine” but In my installation I don’t see the issue..

WIndows 10 PowerShell “curl”:

 ![image](https://help.nextcloud.com/uploads/default/original/3X/3/c/3ce86f5d30d9190b5b7c8953ba96113eb6f68bdf.png)

I don’t see any issue on your configs at first glance.. consider providing more configs and logs

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_[View the full topic](https://help.nextcloud.com/t/dns-errors-and-could-not-check-for-javascript-support-in-docker-instance/188438)._