Now, we have to create the backend pool for the application gateway and assign port 80 to it, so that it can be accessed by the application gateway. Take the following steps:

1. Create the backend pool and settings, as follows:

$address1 = Get-AzNetworkInterface -ResourceGroupName PacktApplicationGateway -Name PacktNic1
$address2 = Get-AzNetworkInterface -ResourceGroupName PacktApplicationGateway -Name PacktNic2

$backendPool = New-AzApplicationGatewayBackendAddressPool `
  -Name PacktGBackendPool `
  -BackendIPAddresses $address1.ipconfigurations[0].privateipaddress, $address2.ipconfigurations[0].privateipaddress

$poolSettings = New-AzApplicationGatewayBackendHttpSettings `
  -Name PacktPoolSettings `
  -Port 80 `
  -Protocol Http `
  -CookieBasedAffinity Enabled `
  -RequestTimeout 120

2. Next, we need to create the listener and add a rule. A listener is required to allow the application gateway to route the traffic appropriately to the backend pool. First we need to create a new listener and assign the frontend configuration and frontend port that we created previously to it. Then, we need to create a rule, which is required for the listener to know which backend pool is used for the incoming traffic. Create the listener and add the rule, as follows:

$defaultlistener = New-AzApplicationGatewayHttpListener `
  -Name PacktAGListener `
  -Protocol Http `
  -FrontendIPConfiguration $fipconfig `
  -FrontendPort $frontendport
$frontendRule = New-AzApplicationGatewayRequestRoutingRule `
  -Name rule1 `
  -RuleType Basic `
  -HttpListener $defaultlistener `
  -BackendAddressPool $backendPool `
  -BackendHttpSettings $poolSettings