June 11, 2015 Leave a comment
The most common use for Web Roles is to host web workloads that are accessible from the public internet, but for enterprises a common requirement is to deploy load balanced web workloads that are only accessible from within their network (the Azure VNET and, in many cases, from on-premises via ExpressRoute) Turns out that this is quite easy to achieve, but perhaps not well known – To achieve this, two additions are needed in the cloud service project’s configuration file. Firstly – in the service definition file the web role is likely to have an InputEndpoint, to connect the endpoint to the internal load balancer one can add the loadBalancerName attribute –
<Endpoints> <InputEndpoint name=”Endpoint1″ protocol=”http” port=”80″ loadBalancer=”MyIntranetILB” /> </Endpoints>
Then, in the service configuration file one has to link the web role to a subnet and corresponding vnet and provide the details around the load balancer, this is done by adding the following section after the Role element within the ServiceConfiguration Element –
<NetworkConfiguration> <VirtualNetworkSite name=”[vnet name]” /> <AddressAssignments> <InstanceAddress roleName=”[role name]”> <Subnets> <Subnet name=”[subnet name]” /> </Subnets> </InstanceAddress> </AddressAssignments> <LoadBalancers> <LoadBalancer name=”MyIntranetILB”> <FrontendIPConfiguration type=”private” subnet=”[subnet name]” staticVirtualNetworkIPAddress=”172.24.19.46″ /> </LoadBalancer> </LoadBalancers> </NetworkConfiguration>
Notice that you can (optionally) add a static ip for the load balancer – this is important as you’re likely to want to configure a DNS entry for this There is no need to create anything in advance other than the VNET and the Subnet – the internal load balancer will be created as part of the deployment. Upon a successful deployment the web role will NOT be accessible via the public internet and you will have a load balanced internal IP to access it from the VNET.
One of the questions I’ve been asked is whether the IP assigned to the ILB in the configuration file is registered with the DHCP server, and the answer appears to be yes. when I’ve configured an IP address right at the beginning on the subnet, the web roles and other VMs provisioned later on the network, were assigned IP addresses greater than the load balancer, so one does not have to worry about IP clashes when configuring an ILB in this fashion.