Learn Cloud NetAzure networking, beginner to advanced0 XP0/80
Intermediate · Name resolution · 14 of 15

Private endpoint name doesn't resolve

Problem

stlogs02.blob.core.windows.net doesn't resolve from vm-spoke1.

Your job
  • Make stlogs02.blob.core.windows.net resolve to 10.0.3.5 from vm-spoke1
Without breaking
  • Keep stlogs01 resolving to 10.0.3.4broken
Background

A second storage account, stlogs02, got its own private endpoint, pe-stlogs02, in vnet-hub at 10.0.3.5, next to stlogs01's at 10.0.3.4. Public network access is disabled on both. From vm-spoke1 in the peered vnet-spoke1, stlogs01 works fine, but stlogs02.blob.core.windows.net doesn't resolve at all. The privatelink.blob.core.windows.net zone is linked to both networks. Working means the stlogs02 name gives vm-spoke1 its private IP.

How to work it
  1. 1See it fail

    Prove the problem yourself before you change anything. Reports are often wrong.

    VM commands forVMs
    1. ssh vm-spoke1
      What's this?

      Opens a shell on vm-spoke1, so the next commands run on that VM. In this lab it's a shortcut. In real Azure you'd connect through something like Azure Bastion, or SSH to an address you can reach.

    2. nslookup stlogs02.blob.core.windows.net
      What's this?

      Asks the VM's DNS server what IP address a name points to. Run it on the VM that has the problem, because each VM can get a different answer.

    3. nc -zv stlogs02.blob.core.windows.net 443
      What's this?

      netcat, a standard Linux tool. Tries to open a TCP connection and reports whether it worked.

      • -z only check whether the port answers. Send no data
      • -v print the result in words
      • stlogs02.blob.core.windows.net where to connect
      • 443 the port to try

    Ticks off when the test runs on vm-spoke1.

  2. 2Find where it stops
  3. 3Name the cause
  4. 4Fix it and test again
  5. 5Explain it
Sources on Microsoft Learn (2)
Troubleshoot private endpoint DNS resolutionAzure Private Endpoint DNS integration
0/1 changes
Network map
?
  • Resource group, the outer dashed frame
  • Virtual network, with its address space top right
  • Subnet, with range and usable IPs (5 reserved)
  • Network security group. A small shield on a VM's NIC means the NIC has one too
  • Route table on the subnet
  • NICVM Appliance Private endpoint
  • Peering Connected Initiated or access off
  • Goal working Goal broken, X marks where it stops
  • Private DNS zone, dotted lines go to linked VNets
  • Orange pulse: what your last command changed. Drag to pan, Ctrl and scroll to zoom.
Resource grouprg-labvnet-spoke1: tap to inspectVirtual networkvnet-spoke110.1.0.0/16subnet-app: tap to inspectsubnet-app10.1.1.0/24 · 251 usablevm-spoke1 10.1.1.4: tap to inspectNICvm-spoke110.1.1.4vnet-hub: tap to inspectVirtual networkvnet-hub10.0.0.0/16subnet-pe: tap to inspectsubnet-pe10.0.3.0/24 · 251 usablepe-stlogs01 10.0.3.4: tap to inspectpe-stlogs0110.0.3.4pe-stlogs02 10.0.3.5: tap to inspectpe-stlogs0210.0.3.5Connected: tap to inspectpeeredprivatelink.blob.core.windows.net: tap to inspectDNSPrivate DNS zone · privatelink.blob.core.windows.net · 2 links · stlogs01 → 10.0.3.4stlogs02.blob.core.windows.net?:443 ✗
  • vm-spoke1 → stlogs02.blob.core.windows.net:443should work: not working
Goals 0/3
Cloud Shell · bashVMsrg-lab · eastus2
cloudshell:~$