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[GH-ISSUE #2368] Does CNAME destinations work? #1676

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opened 2026-02-26 07:31:59 +03:00 by kerem · 5 comments

kerem commented

2026-02-26 07:31:59 +03:00

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Originally created by @pszypowicz on GitHub (Nov 4, 2022).
Original GitHub issue: https://github.com/NginxProxyManager/nginx-proxy-manager/issues/2368

Checklist

Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
- Yes
Are you sure you're not using someone else's docker image?
- Yes
Have you searched for similar issues (both open and closed)?
- Yes

Describe the bug

I have 2 entries in my dns server:
sub1.domain.com -> CNAME sub2.domain.com
sub2.domain.com -> A record 192.168.0.2

I can get IP's of both from the shell of NPM container:

$ getent hosts sub2.domain.com
192.168.0.2 sub2.domain.com
$ getent hosts sub1.domain.com
192.168.0.2 sub2.domain.com sub1.domain.com

I'm configuring Proxy Host.

When I will configure destination to point to sub2.domain.com, everything works.

But when I'm using sub1.domain.com I see following error in the error_log:

sub1.domain.com could not be resolved (3: Host not found)

Nginx Proxy Manager Version

v2.9.18

To Reproduce
Steps to reproduce the behavior:

Configure the destination
Visit site in broswer, get 502
Check the error_log and see Host not found

Expected behavior

Site should work

Operating System

Synology docker

NPM container with macvlan
A record points to synology macvlan shim interface

Additional context

DNS is handled with Adguard DNS rewrites

Originally created by @pszypowicz on GitHub (Nov 4, 2022). Original GitHub issue: https://github.com/NginxProxyManager/nginx-proxy-manager/issues/2368  **Checklist** - Have you pulled and found the error with `jc21/nginx-proxy-manager:latest` docker image? - Yes - Are you sure you're not using someone else's docker image? - Yes - Have you searched for similar issues (both open and closed)? - Yes **Describe the bug**  I have 2 entries in my dns server: sub1.domain.com -> CNAME sub2.domain.com sub2.domain.com -> A record 192.168.0.2 I can get IP's of both from the shell of NPM container: ```sh $ getent hosts sub2.domain.com 192.168.0.2 sub2.domain.com $ getent hosts sub1.domain.com 192.168.0.2 sub2.domain.com sub1.domain.com ``` I'm configuring Proxy Host. When I will configure destination to point to sub2.domain.com, everything works. But when I'm using sub1.domain.com I see following error in the error_log: ``` sub1.domain.com could not be resolved (3: Host not found) ``` **Nginx Proxy Manager Version**  v2.9.18 **To Reproduce** Steps to reproduce the behavior: 1. Configure the destination 2. Visit site in broswer, get 502 3. Check the error_log and see `Host not found` **Expected behavior**  Site should work **Operating System**  Synology docker - NPM container with macvlan - A record points to synology macvlan shim interface **Additional context**  DNS is handled with Adguard `DNS rewrites`

kerem

2026-02-26 07:31:59 +03:00

closed this issue
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kerem commented

2026-02-26 07:32:00 +03:00

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@skirven4 commented on GitHub (Nov 6, 2022):

I have a CNAME set up, and it works fine. Do you have a valid entry in NPM that would resolve to your sub1.domain.com and would be accessible from the same location where you NPM is residing?

@skirven4 commented on GitHub (Nov 6, 2022): I have a CNAME set up, and it works fine. Do you have a valid entry in NPM that would resolve to your sub1.domain.com and would be accessible from the same location where you NPM is residing?

kerem commented

2026-02-26 07:32:00 +03:00

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Owner

@the1ts commented on GitHub (Nov 6, 2022):

What DNS server is in /data/nginx/resolvers.conf I think this is made at first start and if you have changed DNS servers since perhaps that needs updating. i.e. the NPM container and the Nginx may use different DNS servers for the lookup giving you the differing results you are seeing.
The container (/etc/resolv.conf) probably uses 127.0.0.11 so points to the docker service which combines both docker hosted container names and forwards to the host to lookup requests external to docker.

@the1ts commented on GitHub (Nov 6, 2022): What DNS server is in /data/nginx/resolvers.conf I think this is made at first start and if you have changed DNS servers since perhaps that needs updating. i.e. the NPM container and the Nginx may use different DNS servers for the lookup giving you the differing results you are seeing. The container (/etc/resolv.conf) probably uses 127.0.0.11 so points to the docker service which combines both docker hosted container names and forwards to the host to lookup requests external to docker.

kerem commented

2026-02-26 07:32:00 +03:00

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Owner

@pszypowicz commented on GitHub (Mar 4, 2023):

I found some time to reproduce the problem again and investigate it deeper.

I do not have /data/nginx/resolvers.con file, but I found that file in /etc/nginx/conf.d/include and it looks like this

[root@docker-7e906569418d:/etc/nginx/conf.d/include]# cat resolvers.conf
resolver 127.0.0.11  valid=10s;
[root@docker-7e906569418d:/etc/nginx/conf.d/include]# cat /etc/resolv.conf
nameserver 127.0.0.11
options ndots:0

So it looks like they both use the same dns server?

@pszypowicz commented on GitHub (Mar 4, 2023): I found some time to reproduce the problem again and investigate it deeper. I do not have `/data/nginx/resolvers.con` file, but I found that file in `/etc/nginx/conf.d/include` and it looks like this ``` [root@docker-7e906569418d:/etc/nginx/conf.d/include]# cat resolvers.conf resolver 127.0.0.11 valid=10s; [root@docker-7e906569418d:/etc/nginx/conf.d/include]# cat /etc/resolv.conf nameserver 127.0.0.11 options ndots:0 ``` So it looks like they both use the same dns server?

kerem commented

2026-02-26 07:32:00 +03:00

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@github-actions[bot] commented on GitHub (Feb 6, 2024):

Issue is now considered stale. If you want to keep it open, please comment 👍

@github-actions[bot] commented on GitHub (Feb 6, 2024): Issue is now considered stale. If you want to keep it open, please comment :+1:

kerem commented

2026-02-26 07:32:00 +03:00

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@github-actions[bot] commented on GitHub (Mar 22, 2025):

Issue was closed due to inactivity.

@github-actions[bot] commented on GitHub (Mar 22, 2025): Issue was closed due to inactivity.

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starred/nginx-proxy-manager-NginxProxyManager#1676

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