Tutorial / Cram Notes
Virtual network connectivity issues in Azure can be a stumbling block for even the most experienced Azure administrators. This article will guide you through the common troubleshooting steps for virtual network connectivity, which are relevant for the AZ-104 Microsoft Azure Administrator exam.
Check Virtual Network Configuration:
The first step in troubleshooting is to ensure that the virtual network and its related components are configured correctly. Verify the following elements:
- Virtual Network (VNet) Settings: Ensure that the VNet’s address space does not overlap with any other VNet you wish to connect. CIDR (Classless Inter-Domain Routing) notation must correctly define the address range.
- Subnet Configuration: Check if the subnets are correctly defined and associated with the right network interfaces. Also, make sure that the subnet addresses are within the VNet’s address space.
- Network Security Group (NSG) Rules: NSGs are used to allow or deny traffic to network interfaces (NIC), VMs, and subnets. Ensure that the rules are set to permit the intended traffic.
- Route Tables: Route tables contain a set of rules, called routes, that determine where network traffic from a subnet or virtual network interface is routed. Ensure that these rules are not misconfigured leading to unintended traffic flow.
Verify Connectivity with Network Watcher:
Azure Network Watcher provides tools to monitor, diagnose, and gain insights into network performance and health. Utilize the following features:
- IP Flow Verify: This checks if a packet is allowed or denied to or from a virtual machine. Input the local IP address, remote IP address, port, protocol, and direction (inbound or outbound) to verify.
- Next Hop: Determines the next hop for packets routed in the Azure VNet, which helps in understanding the path taken by the traffic.
- Connection Troubleshoot: Tests the connection between a VM and another VM, an FQDN, a URI, or an IPv4 address. It reports on phase issues, latency, and detected network errors.
Utilize Azure Resource Health and Service Health Dashboard:
Azure Resource Health provides personalized information about the health of your Azure resources. Check this for any known issues with the Azure platform that may be affecting your virtual network connectivity.
The Service Health dashboard provides a view of the health of Azure services across regions. If there is a known issue with Azure services that could impact networking, it will be listed here.
Common Connectivity Issues and Resolutions:
| Issue Description | Possible Cause | Resolution |
|---|---|---|
| VMs cannot communicate over the VNet | Misconfigured NSG rules or route tables | Adjust NSG settings, Check Route Tables |
| Cross-VNet connection not working | Overlapping address spaces, Missing peering | Ensure unique address spaces, Configure VNet Peering |
| Unable to connect to VM with RDP/SSH | NSG blocking RDP/SSH port | Update NSG to allow RDP (Port 3389) or SSH (Port 22) |
| Connectivity issues to DNS servers | Incorrect DNS server or settings | Verify DNS settings and VM’s DNS configuration |
| Slow network performance | Insufficient bandwidth or size of VM | Scale network resources or VM size |
Advanced Troubleshooting Techniques:
For advanced issues, you may need to delve deeper:
- Packet Capture: Network Watcher can capture packets flowing to and from a VM. Analyzing these packets can help identify traffic patterns and potential security issues.
- Azure Monitor Logs: Collect and analyze network performance metrics with Azure Monitor logs to understand long-term patterns and identify intermittent problems.
- VPN and ExpressRoute Troubleshooting: For hybrid connections using VPN or ExpressRoute, ensure that all connections are established, and no misconfigurations exist on the Azure and on-premises sides.
- Application Gateway / Load Balancer Health Probes: For issues related to resources behind these services, ensure the health probes are configured correctly and check the probe status.
In conclusion, isolating and resolving virtual network connectivity issues in Azure involves a strategic approach to configuration validation, tool utilization, and understanding both common and complex issues. As an Azure Administrator preparing for the AZ-104 exam, mastering these troubleshooting techniques will not only help in passing the exam but also effectively manage Azure environments in real-world scenarios.
Practice Test with Explanation
True or False: NSG (Network Security Group) rules do not affect virtual network connectivity within the same subnet.
- False
NSG rules can affect virtual network connectivity within the same subnet by allowing or denying traffic to and from resources within that subnet.
When a virtual machine cannot communicate with other resources on the same virtual network, what should you check first?
- A) Route table configurations
- B) Guest OS firewall settings
- C) NSG (Network Security Group) rules
- D) Azure service status
C) NSG (Network Security Group) rules
When facing connectivity issues between resources on the same virtual network, the first thing to check is Network Security Group rules, as they define the allowed and denied traffic within the network.
True or False: Azure automatically creates a system route that enables communication within a virtual network.
- True
Azure automatically creates system routes that enable communication within a virtual network, between virtual networks, on-premises networks, and the Internet.
What is the purpose of a User Defined Route (UDR) in Azure?
- A) To define DNS settings
- B) To override Azure’s default system routes
- C) To set up NSG rules
- D) To monitor network traffic
B) To override Azure’s default system routes
User Defined Routes are used to override Azure’s default system routes to customize network traffic flow within and between subnets.
True or False: You can use Azure Network Watcher’s IP flow verify tool to diagnose resource network traffic filters that might be blocking communication.
- True
The Azure Network Watcher’s IP flow verify tool can be used to diagnose if network security groups (NSGs) or other network traffic filters are blocking communication to or from a virtual machine.
Which Azure tool should you use to troubleshoot connectivity issues from the internet to Azure virtual machines?
- A) Azure Service Health
- B) Azure Traffic Manager
- C) Azure Network Watcher’s Connection Troubleshoot
- D) Azure Monitor
C) Azure Network Watcher’s Connection Troubleshoot
Azure Network Watcher’s Connection Troubleshoot tool helps to diagnose connectivity issues from the internet to Azure virtual machines.
True or False: The effective routes for a network interface (NIC) in Azure display both the system and user-defined routes that apply.
- True
The effective routes for a network interface in Azure give you the combined list of system and user-defined routes that are applied to the NIC.
If two virtual machines are in different regions but within the same virtual network, they can communicate without the need for a Virtual Network Gateway.
- A) True
- B) False
B) False
Virtual machines in different Azure regions but within the same virtual network will need a Virtual Network Gateway or a similar mechanism such as VNet Peering or VPN Gateway to enable communication between them.
True or False: Azure virtual machines can be connected to Azure Virtual Networks only during their creation.
- False
Azure virtual machines can be connected to, or removed from, Azure Virtual Networks both during their creation and after they have been provisioned.
Which feature of Azure Network Watcher allows the visualization of network topology for troubleshooting?
- A) NSG Flow Logs
- B) Connection Monitor
- C) Traffic Analytics
- D) Topology
D) Topology
The Topology feature of Azure Network Watcher allows visualization of network resources and their relationships, aiding troubleshooting of network structure and connectivity issues.
True or False: You can use Azure Network Watcher’s VPN Diagnostics to troubleshoot connectivity issues for site-to-site VPN connections.
- True
Azure Network Watcher provides VPN Diagnostics that enable administrators to troubleshoot connectivity issues for site-to-site VPN connections.
When troubleshooting a subnet’s connectivity to the internet, what is one of the most common causes for the lack thereof?
- A) Incorrectly configured load balancers
- B) Missing a route to the internet in the route table
- C) Virtual machine size limitations
- D) Inadequate subscription permissions
B) Missing a route to the internet in the route table
A common cause for a subnet’s inability to connect to the internet is a missing route to the internet, which can be resolved by verifying and adjusting the route table configurations as needed.
Interview Questions
What is Azure Network Watcher?
Azure Network Watcher is a cloud-based service that provides a suite of network monitoring and troubleshooting tools for Microsoft Azure. It helps to monitor, diagnose, and gain insights into the network performance and health of your virtual machines, subnets, and network security groups.
How can Azure Network Watcher help to troubleshoot virtual network connectivity issues?
Azure Network Watcher can help to troubleshoot virtual network connectivity issues by providing diagnostic tools such as the Connectivity Check and the IP Flow Verify, which allow you to test and diagnose connectivity between virtual machines, subnets, and network security groups.
What is the Connectivity Check tool in Azure Network Watcher?
The Connectivity Check tool in Azure Network Watcher is a feature that allows you to test connectivity between a source virtual machine and a target virtual machine, subnet, or endpoint. It helps you to quickly identify if there is a connectivity issue between the source and target.
What is the IP Flow Verify tool in Azure Network Watcher?
The IP Flow Verify tool in Azure Network Watcher is a feature that allows you to test connectivity between a source and target virtual machine or between a source virtual machine and an endpoint using the IP protocol. It helps you to diagnose the flow of traffic and identify where connectivity is being blocked.
How can you use Azure Network Watcher to monitor network traffic?
You can use Azure Network Watcher to monitor network traffic by enabling the Traffic Analytics feature. This feature provides insights into traffic flow patterns, top talkers, and network security group (NSG) rule effectiveness. You can also configure NSG flow logs, which capture the IP traffic flowing through an NSG, and send them to Azure Storage, Log Analytics, or Event Hubs for analysis.
What is the Network Watcher Agent?
The Network Watcher Agent is an optional lightweight software component that can be installed on virtual machines in a virtual network. It allows you to collect packet captures, perform network latency tests, and monitor network health and performance. The Network Watcher Agent is useful for diagnosing complex connectivity issues and troubleshooting virtual network configurations.
What is the Network Performance Monitor?
The Network Performance Monitor is a feature in Azure Network Watcher that provides real-time network monitoring and diagnostic capabilities. It allows you to monitor the health and performance of your network infrastructure, including virtual machines, load balancers, and VPN gateways. You can use the Network Performance Monitor to detect and diagnose network issues, such as latency, packet loss, and connectivity issues.
What is the Next Hop tool in Azure Network Watcher?
The Next Hop tool in Azure Network Watcher allows you to identify the next hop for a given traffic flow between two virtual machines or between a virtual machine and an endpoint. It helps you to diagnose connectivity issues and identify where traffic is being dropped or routed incorrectly.
How can you use Azure Network Watcher to troubleshoot VPN connections?
You can use Azure Network Watcher to troubleshoot VPN connections by using the VPN Troubleshoot feature. This feature provides a step-by-step troubleshooting guide that helps you diagnose and resolve issues with your virtual network gateway, connection, or on-premises network configuration.
What is the Network Topology tool in Azure Network Watcher?
The Network Topology tool in Azure Network Watcher provides a visual representation of your virtual network topology. It allows you to view the relationships between virtual machines, subnets, and network security groups, and to identify any misconfigurations or connectivity issues. You can use the Network Topology tool to troubleshoot virtual network connectivity and to ensure that your network is properly configured.
I’m having trouble connecting my virtual network to the on-premises network. Any tips?
Appreciate the details shared in this blog post. Very helpful!
Even after following the steps, I can’t ping my VMs. What could be wrong?
How do I diagnose traffic flow issues in my virtual network?
It’s disappointing that the blog doesn’t cover NSG configurations in detail.
Thanks for the blog! Exactly what I was looking for.
What are the best practices for VNet peering configurations?
I managed to resolve my VNet issues after reading this. Thanks!