HTTPS blocked despite an allow rule
vm-client times out connecting to vm-web on 443.
- Get vm-client reaching vm-web on 443
- Keep SSH (22) from vm-client to vm-web blockedbroken
Background
vm-web (10.1.1.4) hosts the web app, and vm-client (10.1.2.4) in subnet-client uses it over HTTPS on 443. After a security lockdown on nsg-web, vm-client can't reach it anymore. The security team says they added an allow rule for 443 from subnet-client, and it still fails. Working means vm-client gets in on 443 while SSH (22) from vm-client stays blocked. Find out why, and fix it without opening anything extra.
- 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 10.1.1.4 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 words10.1.1.4where to connect443the 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)
?
- 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-web:443should work: not workingvm-client → vm-web:22should stay blocked: blocked