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Chapter 15 · Azure Diagnostics
Subchapter 15.30
troubleshooting/compute/references/network-connectivity.mdMarkdown3 KBView on GitHub
Use when the VM is running but unreachable due to Azure network configuration: NSG, routing, NIC, public IP, or DNS.
| Symptom | OS | Action | Docs |
|---|---|---|---|
| no NSG allow for RDP/SSH | Any | Add inbound TCP 3389/22 from approved source | RDP NSG (opens in a new tab) |
| NIC and subnet NSGs conflict | Any | Traffic must pass both; inspect effective rules | Traffic filter (opens in a new tab) |
| UDR sends traffic to NVA | Any | Check effective routes and NVA forwarding | Routing (opens in a new tab) |
| no public IP | Any | Add public IP or use Bastion/private path | Public IP (opens in a new tab) |
| guest NIC disabled/down | Windows/Linux | Enable NIC via Run Command or Serial Console | RDP NIC (opens in a new tab) / SSH overview (opens in a new tab) |
| static guest IP misconfig | Windows/Linux | Restore DHCP guest config | Reset NIC (opens in a new tab) / SSH overview (opens in a new tab) |
| ghost NIC after disk swap/resize | Windows | Reset network interface | Reset NIC (opens in a new tab) |
| DNS failure | Any | Check DNS; Azure default is 168.63.129.16 | DHCP (opens in a new tab) |
az network nic list-effective-nsg --name <nic> -g <rg>
az network nic show-effective-route-table --name <nic> -g <rg> -o table
az vm list-ip-addresses --name <vm> -g <rg> -o table
az network watcher test-connectivity --source-resource <vm-resource-id> \
--dest-address <ip> --dest-port <port> -g <rg>Linux guest NIC commands use VM agent/extensions. Run Pre-Flight Safety Checks first.
az vm repair reset-nic --name <vm> -g <rg> --yes
az vm run-command invoke --name <vm> -g <rg> --command-id RunShellScript \
--scripts "ip link show; ip addr show; ip link set eth0 up && dhclient eth0"