Intermediate · Review · 15 of 15

Review: spoke can't reach a hub API

Problem

vm-spoke1 can't reach the reporting API on vm-hub at 443.

Your job
  • Get vm-spoke1 reaching vm-hub on 443
Without breaking
  • Keep SSH (22) from vm-spoke1 to vm-hub blockedbroken
Background

vm-spoke1 (10.1.1.4, in vnet-spoke1) needs the reporting API on vm-hub (10.0.1.4, in vnet-hub) on port 443. The peering between the two networks shows Connected, and nsg-shared on vm-hub's subnet already allows 443 from vnet-spoke1. It still fails. More than one thing is wrong. Working means 443 gets through while SSH (22) from vm-spoke1 stays closed.

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. nc -zv 10.0.1.4 443
      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
      • 10.0.1.4 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
Sources on Microsoft Learn (3)
0/2 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-shared: tap to inspectsubnet-shared10.0.1.0/24 · 251 usablensg-sharedvm-hub 10.0.1.4: tap to inspectNICvm-hub10.0.1.4Connected, VNet access off: tap to inspectno access:443 ✗
  • vm-spoke1 → vm-hub:443should work: not working
  • vm-spoke1 → vm-hub:22should stay blocked: blocked
Goals 0/2
Cloud Shell · bashVMsrg-lab · eastus2
cloudshell:~$