Spoke can't resolve on-premises names
vm-spoke1 can't resolve app.corp.contoso.com.
- Make app.corp.contoso.com resolve to 192.168.10.5 from vm-spoke1
- Get vm-spoke1 reaching app.corp.contoso.com on 443broken
Background
The app on vm-spoke1 needs app.corp.contoso.com, which only the on-premises DNS server dns-onprem at 192.168.10.10 knows. The hub's resolver dnspr-hub has an outbound endpoint and a forwarding ruleset, rs-onprem, with a rule for corp.contoso.com, copied from the old design. Nobody can resolve the name yet, and vm-spoke1 is where it's needed.
- 1See it fail
Prove the problem yourself before you change anything. Reports are often wrong.
VM commands forVMsssh vm-spoke1What'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.
nslookup app.corp.contoso.comWhat'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.
nc -zv app.corp.contoso.com 443What's this?
netcat, a standard Linux tool. Tries to open a TCP connection and reports whether it worked.
-zonly check whether the port answers. Send no data-vprint the result in wordsapp.corp.contoso.comwhere to connect443the port to try
Ticks off when the test runs on vm-spoke1.
- 2Find where it stops
- 3Name the cause
- 4Fix it and test again
- 5Explain it
Sources on Microsoft Learn (3)
?
- 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
- VM 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.
vm-spoke1 → app.corp.contoso.com:443should work: not working