A Weird Networking Problem with Azure SQL Database (and Fios)

Published On: 2020-04-20By:

Note: This is my first blog post in a while. You too may have been stressed by recent events in world. I’m also doing a large content project I’ll hope you get to enjoy in the near future too. This post actually ties into working from home.

 

pexels-photo-373543

So anyway, one of our customers recently spun up a new Azure SQL Database in the Azure South Africa North region, and two of their team members couldn’t connect to it from their homes. The common element–both of them used Verizon Fios as their ISP.

It’s important to note that connectivity for Azure SQL Database is to a public IP address. Each region has a public IP address and a lookup takes place, and then you are connected through a gateway and you eventually connect to the database. The IP address is just a public endpoint. If I run a trace route to a database running in the Azure US East region I see:

Josephs-MacBook-Pro-3:Dropbox joey$ traceroute dcac-demo.database.windows.net
traceroute to cr4.eastus2-a.control.database.windows.net (52.167.104.0), 64 hops max, 52 byte packets
1 192.168.115.1 (192.168.115.1) 2.224 ms 2.849 ms 1.953 ms
2 96.120.76.77 (96.120.76.77) 12.961 ms 12.978 ms 14.438 ms
3 68.86.213.153 (68.86.213.153) 10.461 ms 9.803 ms 8.983 ms
4 68.86.211.170 (68.86.211.170) 16.069 ms 6.967 ms 12.133 ms
5 68.85.158.49 (68.85.158.49) 11.460 ms 15.657 ms 11.314 ms
6 be-201-ar03.ivyland.pa.panjde.comcast.net (96.108.181.21) 14.815 ms 13.470 ms 13.775 ms
7 be-33287-cr01.newark.nj.ibone.comcast.net (68.86.93.173) 18.519 ms 17.500 ms 19.012 ms
8 be-1301-cs03.newark.nj.ibone.comcast.net (96.110.36.89) 16.457 ms 23.452 ms 20.628 ms
9 be-2303-pe03.newark.nj.ibone.comcast.net (96.110.37.74) 15.248 ms 21.317 ms 22.250 ms
10 50.248.118.226 (50.248.118.226) 16.467 ms 18.986 ms 23.555 ms
11 ae23-0.ear01.ewr30.ntwk.msn.net (104.44.239.159) 24.966 ms 22.497 ms
ae24-0.ear01.nyc30.ntwk.msn.net (104.44.239.155) 26.774 ms
12 be-21-0.ibr02.ewr30.ntwk.msn.net (104.44.20.122) 32.792 ms
be-20-0.ibr01.nyc30.ntwk.msn.net (104.44.20.124) 27.437 ms
be-20-0.ibr01.ewr30.ntwk.msn.net (104.44.20.120) 34.036 ms

You can see that on steps 7-9 it my connection jumps onto the Comcast backbone (ibone.comcast.net) network, and at step 11 jumps onto the Microsoft Azure network (msn.net). I truncated the output of the trace route there.

Monica Rathbun (b|t ) who works with me at DCAC, also had Fios and was able to help us troubleshoot this. When Monica ran a trace route to the public IP address the  of Azure SQL Database in South Africa North it looked like:

C:\Users\monica>Tracert egpaftz.database.windows.net

Tracing route to cr1.southafricanorth1-a.control.database.windows.net [102.133.152.0]

over a maximum of 30 hops:

  1    <1 ms     1 ms    <1 ms  Fios_Quantum_Gateway.fios-router.home [192.168.1.1]

  2     3 ms     1 ms     2 ms  102.133.152.0

That is not how the internet is supposed to work. While we tried to figure out how to get in touch with someone at Verizon to fix this, which through normal consumer channels is not fun. So while we waited for that to get fixed, we had another options to fix this.

Introducing Private Link

Azure Private Link was recently introduced as generally available for Azure SQL Database and allows for you to have a truly private connection to your database. For several years now you have been able to use network endpoints to allow a specific VM or App Service to connect to Azure SQL, however that design had some limitations. The first being that it still routed the connection to the database over the public IP address. The second was that network endpoints did not support multi-region scenarios. With Private Link your database has it’s own private IP address on the virtual network where it is deployed.

In our client’s case, this work around involved connecting to an Azure VPN in US East which would then be connected to South Africa North. One interesting thing about Private Link is that it doesn’t support Azure Virtual Network peering, so you will need to create a Gateway if you want your traffic to traverse virtual networks. Additionally, we were working in two different subcriptions, which mean we had to use the PowerShell from here. Private Link is easy to configure from your Azure SQL server logical server, but be sure you have the right permissions in Azure RBAC. I needed to be granted the network contributor role in order to get the GUI to work.

The Conclusion

I had some issues that were permissions related which delayed our implementation of Private Link, and I was fortunate enough to have some members of the Azure Networking product group helping me out. Since Microsoft and Verizon are technically partners (Verizon is an ExpressRoute partner) they were able to get in touch with some folks as at Verizon, and they were able to resolve the problem. Sort of–the trace routes still look weird, but everyone can connect. Verizon reports that the trace routes from what they can see look normal. Which tells me they are doing something really weird on the router itself with how Azure traffic is routed.

Photo by Pixabay on Pexels.com

 

 

 

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