Azure Traffic Manager for NetScaler Gateway Failover

Azure Traffic Manager is designed to provide traffic routing to various locations based on a ruleset that you specify. It can be used for priority (failover), weighted distribution, performance, and geographic traffic distribution.

The failover option is similar to GSLB – and works in a similar way, so I am going to demonstrate that in this post. I’ve started with the following environment already configured:

  • Two Azure Locations (East US and South Central US), with a VPN between the sites to join the VNETs
  • 1 Domain Controller in each location
  • 1 NetScaler (standalone) in each location
  • 1 Citrix Environment spread across the two locations
  • NetScaler Gateway’s setup in both sites, and NAT’d out using Azure Load Balancer. (So that we have a public IP offering NetScaler Gateway services in both Azure Locations. Have a look at this Blog post if you require guidance on setting this up.)

Azure Lab Diagram

Before we setup the Azure Traffic Manager profile, we need to give our Public IP Addresses a DNS name label. To do this, browse to the Public IPs for your Load Balancers, and then click on “Configuration”. We need to give our Public IP addresses a DNS name label, as this is what Traffic Manager will be using to balance the endpoints.

Azure Public IP configuration

I have two public IPs so I have created two DNS Name Labels and given them appropriate names:

  • desktop-eus-jwnetworks = East US NetScaler Public IP
  • desktop-scus-jwnetworks = South Central US NetScaler Public IP

Next – it’s time to create the Azure Traffic Manager profile!

Traffic Manager profile creation

After we click create, we just need to populate a few basic details:

Traffic Manager profile creation

As you can see – I have given my Traffic Manager a name, selected Priority as the routing method (this gives us the failover in a similar manner to Active/Passive GSLB). Note: there are other options available:

Traffic Manager routing options

See here for an overview of the Traffic Routing Methods. Next – we need to configure some more settings on our Traffic Manager, to ensure that the Monitoring and Traffic Routing are going to work correctly. In the screenshot below I have adjusted the following:

  • DNS TTL – I’ve adjusted this to 60 seconds, this defaults to 300 seconds (5 minutes)
  • Protocol – HTTPS, this is because we are Monitoring the HTTPS NetScaler Gateway
  • Port – 443 as we are using this port for the NetScaler Gateway
  • Path – this is the path to the files that the monitor will be checking for, so in the case of NetScaler Gateway this is /vpn/index.html – if this page is not available then the service will be marked as unavailable.
  • Probing Interval – this is how often the endpoint health is checked. Values are either every 10 seconds or every 30 seconds
  • Tolerated number of failures – this is how many health check failures are tolerated before the endpoint is marked as unhealthy
  • Monitoring timeout – this is the time the monitor will wait before considering the endpoint as unavailable.

For more information on these configuration options – click here.

Traffic Manager configuration

Next – it is time to add our endpoints! To do this, click on Endpoints and then on Add:

Traffic Manager endpoints

We then need to add our Public IP addresses assigned to the Azure Load Balancers (where the NAT rules were created). Note – you will need to do this for BOTH endpoints:

Adding Endpoints to Traffic Manager

Once both are added, you will see the below in the Endpoints screen. Note that both Endpoints are shown as “Online” – this confirms our monitor is detecting the Endpoints as up. Also note that the Endpoints have priority – this means that under normal operation, all traffic will be sent to the “eus-desktop” endpoint (Priority 1), and in the event of a failure of the “eus-desktop” endpoint, all traffic will be directed to the “scus-desktop” Endpoint.

Endpoints

All that is left to do is test – however, first let’s make things neat for our users with a CNAME DNS Record. We are effectively going to CNAME our jwdesktop.trafficmanager.net record to something that users would be able to remember. You can find your record from the overview screen:

Traffic Manager overview

Next up I added a CNAME record in my Azure DNS Zone:

Add DNS Record

Add CNAME Record

Once this is created – we can start testing! But first, a diagram! Below is shown what we now have setup and working:

Solution Diagram

Note: in order to easily distinguish between my two Gateways, I set the EUS Gateway to the X1 theme, and the SCUS Gateway was left on the default NetScaler theme. When accessing https://desktop.jwnetworks.co.uk I am correctly shown the EUS Gateway:

EUS Gateway Test

Bingo – this all looks good to me! Next up, I disabled the Virtual Server for the EUS NetScaler:

Virtual Server Disabled

After around 30 seconds… the Monitor Status shows as Degraded:

[ for those interested in the maths (10 Second Probe interval + 5 second timeout)x1 tolerated failure (so effectively 15×2 attempts at connecting) ]

Endpoint Health

Next I refreshed the Page and we are presented with the SCUS Gateway page:

SCUS Gateway Page

As you can see, during a failure condition (the EUS Gateway vServer being taken down) the Traffic Manager directs traffic to our Priority 2 site, without any intervention from us. Any users would be able to refresh the page and then log back in. This can be used not only for NetScaler Gateway but for many internet facing services – for example OWA, SharePoint etc. There’s a great many services that can benefit from this type of failover and the resiliency that it offers.