11lll's questions

When resolving towards 8.8.8.8 from a local wi-fi or a personal hotspot, etc. it sometimes fails. Responses are received from these Google IP addresses:

74.125.46.10
74.125.112.1
74.125.112.9
74.125.x.x
74.125.z.z
74.125.w.w

But when resolving towards 8.8.8.8 from a server on AWS or DO it always succeeds. The responses are received from different Google IP addresses:

172.253.199.4
172.253.1.194
172.217.33.132

Why is it so?

An idea: Does Google give a higher priority for big customers like AWS or DO vs the public...? Or is there a different explanation?

Additionally:

1. We even made a test subdomain xip.teltel.io which is set up exactly the same way and when resolving that domain towards 8.8.8.8 it works fine every time. The only difference between sip.teltel.io and xip.teltel.io is the load: sip receives our customer's traffic and xip only our test requests.

How can you explain that?

--

2. We captured the traffic by performing a tcpdump (tcpdump udp and port 53) and noticed that when Google fails to resolve, our name servers never receive a request from Google.

--

3. Here you can test the loops for yourself: This fails with "sip" - while true; do dig A 42894078.sip.teltel.io @8.8.8.8; done; This is OK with "xip"- while true; do dig A 42894078.xip.teltel.io @8.8.8.8; done;

Please, can you help us solve this? It seems quite mysterious to us.

Thanks!

We took care of implementing the changes you suggested for sip.teltel.io in our previous questions, but it did not improve.

Subdomain hosted on AWS sometimes doesn't resolve towards 8.8.8.8

8.8.8.8 Fails to resolve our subdomains randomly

8.8.8.8 returns NXDOMAIN randomly for all our subdomains

UPDATE:

1. We even made a test subdomain xip.teltel.io which is set up exactly the same way as sip.teltel.io and when resolving that domain towards 8.8.8.8 it works fine every time. The only difference between sip.teltel.io and xip.teltel.io is the load: sip receives our customer's traffic and xip only our test requests.

How can you explain that?

2. Here is what we also noticed: When resolving towards 8.8.8.8 from a local wi-fi or a personal hotspot, etc. it sometimes fails. Responses are received from these Google IP addresses:

74.125.46.10
74.125.112.1
74.125.112.9
74.125.x.x
74.125.z.z
74.125.w.w

But when resolving towards 8.8.8.8 from a server on AWS or DO it always succeeds. The responses are received from different Google IP addresses:

172.253.199.4
172.253.1.194
172.217.33.132

Does Google give a higher priority for big customers like AWS or DO vs the public...? Or is there a different explanation?

3. We captured the traffic by performing a tcpdump (tcpdump udp and port 53) and noticed that when Google fails to resolve, our name servers never receive a request from Google.

4. Here you can test the loops for yourself:

This sometimes fails with "sip" - while true; do dig A 42894078.sip.teltel.io @8.8.8.8; done;

This is always OK with "xip"- while true; do dig A 42894078.xip.teltel.io @8.8.8.8; done;

Can you help us solve this? It all seems quite mysterious to us.

Thanks!

Recently we've been having sporadic trouble resolving our subdomain towards 8.8.8.8, so we created a second subdomain for testing, with which we are unable to replicate the issue.

Original subdomain - 42894078.sip.teltel.io - fails occasionally through 8.8.8.8 with the error: server can't find 42894078.sip.teltel.io: NXDOMAIN

Testing subdomain - 42894078.xip.teltel.io - resolves fine through 8.8.8.8

xip.teltel.io is configured exactly as sip.teltel.io.

The only difference is that xip.teltel.io is hosted by DigitalOcean, but sip.teltel.io by AWS.

Do you know why one works but the other doesn't?

Our customers make quite a few domain checks towards Google public DNS with the following domains <userid>.sip.teltel.io, but they often fail. To others, like Cloudflare it is always successful.

When we run nslookup in a loop towards 8.8.8.8, about 80% of the time Google fails to resolve. To 1.1.1.1 it is always successful. See below a failed example:

Request:

while :
do
    nslookup 7157599388.sip.teltel.io 8.8.8.8
done

Response:

Server:     8.8.8.8
Address:    8.8.8.8#53

** server can't find 7157599388.sip.teltel.io: NXDOMAIN

Additionally, when doing a dig towards 8.8.8.8 sometimes it fails, sometimes not: Does anyone have an idea why?

Thank you in advance!

We have a lot of users on our VoIP software. The softphone checks each user's domain every minute, users make calls, send messages, etc. the usual VoIP stuff. Each user usually makes DNS checks several times a minute and altogether there are quite a few requests.

We cannot control to which public DNS the end-user tries resolving. When it is to Google public DNS sometimes, randomly it fails. To others like Cloudflare (1.1.1.1) it always works.

We've researched this and the issue is not the amount of DNS checks from the end-user towards Google DNS, which we know has a limit. Actually, the issue is from Google DNS to our Name Server when Google refuses to check the subdomain SOMETIMES. It seems that there is another limit here.

Here is an example of an unsuccessful request towards 8.8.8.8 after a nslookup (the domain exists).

dns.google can't find 7157599388.sip.teltel.io: Non-existent domain

Any idea how to change this limit?

Help will be highly appreciated!

Thank you in advance!