API blocked despite a subnet allow rule
Problem
vm-client times out connecting to vm-api on 8443.
Your job
- Get vm-client reaching vm-api on 8443
Without breaking
- Keep SSH (22) from vm-client to vm-api blockedbroken
Background
vm-api (10.1.3.4) in subnet-api serves an API on port 8443, and vm-client (10.1.2.4) in subnet-client calls it. nsg-subnet-api on subnet-api already allows 8443 from subnet-client, yet vm-client times out. Working means vm-client gets through on 8443 while SSH (22) to vm-api stays blocked.
How to work it
- 1See it fail
Prove the problem yourself before you change anything. Reports are often wrong.
VM commands forVMsssh vm-clientWhat's this?
Opens a shell on vm-client, 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.
nc -zv 10.1.3.4 8443What'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 words10.1.3.4where to connect8443the port to try
Ticks off when the test runs on vm-client.
- 2Find where it stops
- 3Name the cause
- 4Fix it and test again
- 5Explain it
Sources on Microsoft Learn (2)
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
- 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-client → vm-api:8443should work: not workingvm-client → vm-api:22should stay blocked: blocked
Goals 0/3
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