Azure Route Table: A Comprehensive Guide

An Azure route table is essentially a database that contains a set of rules, known as routes, which determine where network traffic is directed in an Azure Virtual Network (VNet).

Each route in the table specifies a destination IP address and the next hop, which is the IP address of the device that should receive the traffic.

Azure route tables can be used to control and manage network traffic flow between subnets, virtual networks, and on-premises networks.

Azure route tables are an essential component of Azure networking, allowing you to define and manage the flow of network traffic across your Azure resources.

Creating a Route Table is a crucial step in setting up an Azure Route Table. You can create up to a certain limit per Azure location and subscription, so be mindful of that.

To create a route table, start by navigating to the Azure portal and selecting "Create a resource." Then, in the search box, enter "Route table" and select it from the results.

When creating a route table, you'll need to provide a name, subscription, resource group, and location. You can also choose to propagate gateway routes or disable them if needed.

Here are the key settings to consider when creating a route table:

Once you've filled in these settings, select "Review + create" and then "Create" to create your new route table.

You can find a list of all the route tables available within your subscription by searching for and selecting Route tables. This will give you a list of all the route tables in your subscription.

To view the details of a route table, go to the Azure portal, search for and select Route tables, and then choose the route table that you want to view details for. In the route table page, you can view the routes in the route table or the subnets the route table is associated to.

The Azure CLI and PowerShell commands to view route table information are az network route-table list and Get-AzRouteTable, respectively. The command to view the details of a route table is az network route-table show.

Here's a summary of the commands to view route table information:

To view the details of a route, go to the Azure portal, search for and select Route tables, and then choose the route table containing the route you want to view details for. In the route table menu bar, choose Routes to see the list of routes, and then select the route you want to view details of.

Managing route table associations is a crucial part of Azure route table management. You can associate a route table to zero or more subnets, but not to virtual networks.

To associate a route table to a subnet, you must do so in the same Azure location and subscription as the route table. This ensures that the route table can effectively manage traffic for the subnet. You can associate a route table to a subnet through the Azure portal or using the Azure CLI or PowerShell.

Here are the tools and commands you can use to associate a route table to a subnet:

Changing a route table is a crucial step in managing route table associations. You can modify an existing route table by adding or removing routes, associating or dissociating it from subnets, or updating its configuration.

To change a route table, you'll need to go to the Azure portal and select the route table you want to modify. From there, you can choose to add routes, remove routes, associate the route table to subnets, or dissociate it from subnets.

The most common changes are to add routes, remove routes, associate route tables to subnets, or dissociate route tables from subnets. You can use the Azure CLI or PowerShell to update a route table.

Here are the specific steps to change a route table:

Note that you can only associate a route table to subnets in virtual networks that exist in the same Azure location and subscription as the route table.

You can now specify a service tag as the address prefix for a user-defined route (UDR) instead of an explicit IP range. This simplifies the complexity of frequent updates to UDRs and reduces the number of routes you need to create.

Service tags represent a group of IP address prefixes from a specific Azure service. Microsoft manages the address prefixes encompassed by the service tag and automatically updates the service tag as addresses change.

With this release, you can create 25 or fewer routes with service tags in each route table. This limited number ensures that service tags are used efficiently and effectively.

Using service tags in routing scenarios for containers is also supported with this release. This feature expands the capabilities of service tags to include container-based routing scenarios.

NSGs act like a firewall, controlling inbound and outbound traffic based on security rules.

NSGs are essential components of Azure networking, serving a distinct function that shouldn't be used interchangeably with Route Tables.

NSGs control traffic, while Route Tables dictate the flow of network traffic within your VNet, offering more granular control over routing paths.

In Azure, NSGs are used to filter traffic, while Route Tables are used to route traffic to the correct destination.

Managing large-scale or complex networks can be complicated and demanding, leading to long SLA’s and prone to human error.

Tufin offers comprehensive solutions for firewall optimization and firewall management.

It enables centralized Azure firewall management, ensuring your Azure Route Tables and NSGs are managed effectively.

Tufin also provides hybrid cloud security solutions, allowing you to enforce consistent security policies across your on-premises and cloud environments.

Tufin brings immense value in managing Azure Networking, especially when dealing with complex networks.

Route Server is a managed solution that automatically provides resiliency at a regional level. This means that if one component fails, another will automatically take its place.

Route Server offers high availability, which is especially important if you're working with sensitive data. This ensures that your implementation is always up and running, even in the event of a failure.

In Azure regions that support availability zones, Route Server provides zone-level redundancy. This means that your implementation will have multiple copies of its components, each in a different zone. For more information about availability zones, see Regions and availability zones.

To delete a route table in Azure, you need to dissociate it from all subnets first. This is a crucial step to avoid any errors during the deletion process.

Azure portal is the best place to manage your route tables, and you can access it by searching for Route tables. From there, you can select the route table you want to delete.

To delete a route table, go to the Azure portal, select Route tables, and then choose the route table you want to delete. After that, select Delete and confirm your action by selecting Yes in the dialog box.

If you're using Azure CLI or PowerShell, you can also delete a route table using the following commands:

Remember to check the Networking limits - Azure Resource Manager for details on the maximum number of routes per route table and subscription.

To create a route table in Azure, you'll need to define the route table name, subscription, resource group, and location. Then, you can start adding routes to your table. Each route requires a name, address prefix (CIDR format), and next hop type.

You can specify a service tag as the address prefix for a user-defined route instead of an explicit IP range. A service tag represents a group of IP address prefixes from a specific Azure service. This support minimizes the complexity of frequent updates to UDRs and reduces the number of routes that you need to create.

You can create a maximum of 25 or fewer routes with service tags in each route table. To create a route table, follow these steps: On the Azure portal menu or from the Home page, select Create a resource.In the search box, enter Route table. When Route table appears in the search results, select it.In the Route table page, select Create.In the Create route table dialog box, enter a name, select a subscription, resource group, and location.

To configure route tables, you'll need to have the right permissions. This can be achieved by being assigned to the Network contributor role or a Custom role with specific actions.

The Network contributor role is one option, but you can also create a Custom role with the necessary actions to manage route tables and routes.

To create a Custom role, you'll need to assign the following actions: Microsoft.Network/routeTables/read, Microsoft.Network/routeTables/write, Microsoft.Network/routeTables/delete, Microsoft.Network/routeTables/join/action, Microsoft.Network/routeTables/routes/read, Microsoft.Network/routeTables/routes/write, and Microsoft.Network/routeTables/routes/delete.

Additionally, you may need the Microsoft.Network/networkInterfaces/effectiveRouteTable/action and Microsoft.Network/networkWatchers/nextHop/action actions to get the effective route table for a network interface and the next hop from a VM, respectively.

Here's a summary of the required actions for a Custom role:

Creating an Azure Route Table is a straightforward process. You'll need to define the route table name, subscription, resource group, and location within the Azure portal. Then, you can start adding routes to your table.

Each route requires a name, address prefix (CIDR format), and next hop type. Next hop types determine the endpoint to which Azure should direct traffic. For example, a Virtual Network Gateway next hop type would direct traffic to an Azure VPN Gateway or ExpressRoute.

You can associate routes with a subnet within your VNet, allowing Azure to route traffic from that subnet according to your defined routes. Remember to save your configurations once you're done.

If you're more comfortable with scripting, you can also use PowerShell or CLI for creating and managing Azure Route Tables.

Here's a brief overview of the required settings for creating a route table:

To create a route table, you can follow these steps: On the Azure portal menu or from the Home page, select Create a resource. In the search box, enter Route table. When Route table appears in the search results, select it. In the Route table page, select Create. In the Create route table dialog box, enter the required settings and select Review + create and then Create to create your new route table.

To determine the next hop type between a virtual machine and another Azure resource, you can use the Network Watcher tool in the Azure portal. This is helpful when troubleshooting routing problems.

You can select the subscription, resource group, and virtual machine you want to test against, as well as the network interface and source IP address. Then, enter the destination IP address to view the next hop for the VM.

The Network Watcher will tell you the next hop type and the ID of the route that routed the traffic. You can also use the Azure CLI or PowerShell to view the next hop using the `az network watcher show-next-hop` and `Get-AzNetworkWatcherNextHop` commands, respectively.

To validate routing between endpoints, you can use an existing network watcher or create a new one. If you don't have a network watcher, you'll need to create one by following the steps in Create a Network Watcher instance.

To determine Azure's routing, you can use the Network Watcher tool. This is helpful when troubleshooting routing problems. You can access the Network Watcher tool by going to the Azure portal and searching for and selecting Network Watcher.

To use the Network Watcher tool, you'll need to select the subscription, resource group, and virtual machine you want to test against. You'll also need to select the network interface you want to test next hop from and enter the destination IP address you want to view the next hop for.

Here are the steps to follow:

After selecting these options, you can select "Next hop" and wait for Azure to tell you the next hop type and the ID of the route that routed the traffic. You can also use the Azure CLI or PowerShell to achieve the same result using the following commands:

Border Gateway Protocol is a key concept in route table routing. It's used to exchange routes between an on-premises network gateway and an Azure virtual network gateway.

You can use BGP with an Azure virtual network gateway, but it depends on the type of gateway you created. If you selected ExpressRoute, you must use BGP to advertise on-premises routes to the Microsoft edge router.

For ExpressRoute, you can't create UDRs to force traffic to the ExpressRoute virtual network gateway. However, you can use UDRs to force traffic from the express route to a network virtual appliance.

With VPN, you have the option to use BGP, but it's not required. If you do choose to use BGP with VPN, you can find more information in the article on BGP with site-to-site VPN connections.

Using BGP with an Azure virtual network gateway adds a separate route to the route table of all subnets in a virtual network for each advertised prefix.

Here are the types of BGP usage for different gateway types:

Route propagation shouldn't be disabled on GatewaySubnet, as it will cause the gateway to malfunction.