Traffic Manager in Azure portal

 Azure Traffic Manager is a DNS-based traffic load balancer. This service allows you to distribute traffic to your public facing applications across the global Azure regions. Traffic Manager also provides your public endpoints with high availability and quick responsiveness.

Traffic Manager uses DNS to direct the client requests to the appropriate service endpoint based on a traffic-routing method. Traffic manager also provides health monitoring for every endpoint. The endpoint can be any Internet-facing service hosted inside or outside of Azure.

Traffic Manager routing methods

Azure Traffic Manager supports six traffic-routing methods to determine how to route network traffic to the various service endpoints. For any profile, Traffic Manager applies the traffic-routing method associated to it to each DNS query it receives. The traffic-routing method determines which endpoint is returned in the DNS response.

The following traffic routing methods are available in Traffic Manager:

• Priority: Select Priority routing when you want to have a primary service endpoint for all traffic. You can provide multiple backup endpoints in case the primary or one of the backup endpoints is unavailable.
• Weighted: Select Weighted routing when you want to distribute traffic across a set of endpoints based on their weight. Set the weight the same to distribute evenly across all endpoints.
• Performance: Select Performance routing when you have endpoints in different geographic locations and you want end users to use the "closest" endpoint for the lowest network latency.
• Geographic: Select Geographic routing to direct users to specific endpoints (Azure, External, or Nested) based on where their DNS queries originate from geographically. With this routing method, it enables you to be in compliance with scenarios such as data sovereignty mandates, localization of content & user experience and measuring traffic from different regions.
• Multivalue: Select MultiValue for Traffic Manager profiles that can only have IPv4/IPv6 addresses as endpoints. When a query is received for this profile, all healthy endpoints are returned.
• Subnet: Select Subnet traffic-routing method to map sets of end-user IP address ranges to a specific endpoint. When a request is received, the endpoint returned will be the one mapped for that request’s source IP address. 

All Traffic Manager profiles have health monitoring and automatic failover of endpoints. Within a Traffic Manager profile, you can only configure one traffic routing method at a time. You can select a different traffic routing method for your profile at any time. Your changes will be applied within a minute without any downtime. 

Here we will test a demo on priority basis. 

First create two web app in two different region.

In the same way you can create another web app (dotnetguru02) in different region. below is both web app. one is in East US and another is in central US.

Create a traffic manager profile with below information. 

Now my traffic manager profile is ready.

Now create endpoint inside traffic manager.

First we need to add primary end point. then we will create failover end point.

Now my both endpoints are ready. 

Now go to traffic manager profile > Overview : copy the DNS name and paste it in browser url. 

you will see the priority1 web app. now disable the priority1 web app and again refresh the browser. you will see the priority 2 web app. 

You can follow ms documents article for more info. https://docs.microsoft.com/en-us/azure/traffic-manager/quickstart-create-traffic-manager-profile