repeated dns request results in no servers could be reached

Question

repeated dns request results in no servers could be reached

Closed this issue 2 months ago · 3 comments

markuman commented 2 months ago

Prerequisites

I have checked the Wiki and Discussions and found no answer
I have searched other issues and found no duplicates
I want to report a bug and not ask a question or ask for help
I have set up AdGuard Home correctly and configured clients to use it. (Use the Discussions for help with installing and configuring clients.)

Platform (OS and CPU architecture)

Linux, AMD64 (aka x86_64)

Installation

GitHub releases or script from README

Setup

On one machine

AdGuard Home version

v0.107.65

Action

Replace the following command with the one you're calling or a
description of the failing action:

nslookup -debug -type=a 'smtpfra7.fortimailcloud.com' '10.114.2.100'

Expected result

Once ADH is startet, it resolves the 48 A records as expected.

nslookup -debug -type=a 'smtpfra7.fortimailcloud.com' '10.114.2.100'
Server:		10.114.2.100
Address:	10.114.2.100#53

------------
    QUESTIONS:
	smtpfra7.fortimailcloud.com, type = A, class = IN
    ANSWERS:
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.227
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.158
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.225
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.233
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.224
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.147
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.226
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.247
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.237
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.151
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.149
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.245
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.254
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.242
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.153
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.229
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.152
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.240
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.143
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.156
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.235
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.232
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.243
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.146
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.157
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.241
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.228
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.145
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.154
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.248
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.236
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.230
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.239
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.246
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.231
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.150
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.148
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.144
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.244
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.141
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.238
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.234
	ttl = 36951
    ->  smtpfra7.fortimailcloud.com
	internet address = 154.52.2.155
	ttl = 36951
    AUTHORITY RECORDS:
    ADDITIONAL RECORDS:
------------
Non-authoritative answer:
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.227
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.158
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.225
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.233
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.224
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.147
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.226
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.247
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.237
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.151
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.149
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.245
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.254
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.242
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.153
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.229
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.152
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.240
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.143
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.156
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.235
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.232
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.243
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.146
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.157
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.241
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.228
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.145
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.154
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.248
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.236
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.230
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.239
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.246
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.231
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.150
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.148
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.144
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.244
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.141
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.238
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.234
Name:	smtpfra7.fortimailcloud.com
Address: 154.52.2.155

Actual result

When it runs a 2nd time, it results in "no servers could be reached.

nslookup -debug -type=a 'smtpfra7.fortimailcloud.com' '10.114.2.100'
;; Truncated, retrying in TCP mode.
;; Connection to 10.114.2.100#53(10.114.2.100) for smtpfra7.fortimailcloud.com failed: timed out.
;; no servers could be reached
;; Connection to 10.114.2.100#53(10.114.2.100) for smtpfra7.fortimailcloud.com failed: timed out.
;; no servers could be reached
;; Connection to 10.114.2.100#53(10.114.2.100) for smtpfra7.fortimailcloud.com failed: timed out.
;; no servers could be reached

Additional information and/or screenshots

Answer 1 · 2025-09-03T09:40:09.000Z

I figured out that the client commands nslookup and host results in the timeout issues - when ADH is hosted on AWS(!).
While dig works fine.
When ADH is hosted outside AWS, nslookup and host works as expected like dig.

Answer 2 · 2025-09-07T22:39:30.000Z

I can't reproduce this at all - I can run nslookup -debug -type=a 'smtpfra7.fortimailcloud.com' 192.168.0.5 500 times and it returns everytime with details.

I expect this is an AWS problem.

If you are sure it's an AdGuardHome problem please reply with more information/details/logs from AdGuardHome or any other details that makes you think it's an AdGuardHome issue.

Answer 3 · 2025-09-10T06:29:36.000Z

The response of the UDP DNS request was >512bytes. So ADH answers with the T flag and the client switch to TCP (EDNS0).
And TCP 53 was not allowed in the security group (firewall) on the AWS EC2 Instance.