Set up a NAT Gateway with Load Balancing

Introduction

In order for NNM to monitor virtual machine instances in a Microsoft Azure Virtual Network, NNM must run on a virtual machine instance that functions as a network address translation (NAT) gateway. A NAT gateway instance routes traffic from internal-only virtual machine instances to the Internet. A NNM installed on a NAT gateway has visibility into the hostnames and private IP addresses of the internal virtual machine instances before the NAT gateway masquerades the source IP address of incoming packets to forward them to the Internet. Microsoft Azure provides a load balancing service that distributes traffic between multiple servers.

This guide shows setting up a NAT gateway in a Microsoft Azure Virtual Network using load balancing.

Before You Begin

Follow the Azure CLI Installation Instructions. Then connect to your subscription from the CLI.

Tip: If you encounter an error in the Azure CLI about the your subscription not being registered to use a namespace, see this section on the common deployment errors page.

Steps

Enable Azure CLI Resource Manager commands.

azure config mode arm
Create a resource group.

In this example, the resource group pvsLbRg is created.

azure group create pvsLbRg eastus

info: Executing command group create

+ Getting resource group pvsLbRg

+ Creating resource group pvsLbRg

info: Created resource group pvsLbRg

data: Name: pvsLbRg

data: Location: eastus

data: Provisioning State: Succeeded

data: Tags: null

data:

info: group create command OK
Create a storage account in the resource group pvsLbRg .

In this example, the storage group pvslbstore is created.

azure storage account create --location eastus --resource-group pvsLbRg --kind Storage --sku-name GRS pvslbstore

info: Executing command storage account create

+ Checking availability of the storage account name

+ Creating storage account

info: storage account create command OK
Create a Virtual Network in the resource group pvsLbRg .

In this example, the Virtual Network is pvsVNet and has the network range 10.240.0.0/16.

azure network vnet create -g pvsLbRg -n pvsVNet -a 10.240.0.0/16 -l eastus

info: Executing command network vnet create

+ Looking up the virtual network "pvsVNet"

+ Creating virtual network "pvsVNet"

data: Name : pvsVNet

data: Type : Microsoft.Network/virtualNetworks

data: Location : eastus

data: Provisioning state : Succeeded

data: Address prefixes:

data: 10.240.0.0/16

info: network vnet create command OK
Create a Load Balancer.

In this example, the Load Balancer is pvsLb.

azure network lb create pvsLbRg pvsLb eastus

info: Executing command network lb create

+ Looking up the load balancer "pvsLb"

+ Creating load balancer "pvsLb"

data: Name : pvsLb

data: Type : Microsoft.Network/loadBalancers

data: Location : eastus

data: Provisioning state : Succeeded

info: network lb create command OK
Create a public IP and sub domain name for the Load Balancer front end pool.

In this example, the sub domain name is examplelbsubdomain and the public IP is pvsPIP.

azure network public-ip create -d examplelbsubdomain pvsLbRg pvsLbPIP eastus

info: Executing command network public-ip create

warn: Using default --idle-timeout 4

warn: Using default --allocation-method Dynamic

warn: Using default --ip-version IPv4

+ Looking up the public ip "pvsLbPIP "

+ Creating public ip address "pvsLbPIP "

data: Name : pvsLbPIP

data: Type : Microsoft.Network/publicIPAddresses

data: Location : eastus

data: Provisioning state : Succeeded

data: Allocation method : Dynamic

data: IP version : IPv4

data: Idle timeout in minutes : 4

data: Domain name label : examplelbsubdomain

data: FQDN : examplelbsubdomain.eastus.cloudapp.azure.com

info: network public-ip create command OK
Create a front end IP pool and associate it with the public IP pvsLbPIP.

In this example, the frontend pool is named pvsFrontEndPool.

azure network lb frontend-ip create pvsLbRg pvsLb pvsFrontendPool -i pvsLbPIP

info: Executing command network lb frontend-ip create

+ Looking up the load balancer "pvsLb"

+ Looking up the public ip "pvsLbPIP"

+ Updating load balancer "pvsLb"

data: Name : pvsFrontendPool

data: Provisioning state : Succeeded

data: Private IP allocation method : Dynamic

info: network lb frontend-ip create command OK
Create a back end IP pool.

In this example, the back end pool is pvsLbBackendPool.

azure network lb address-pool create pvsLbRg pvsLb pvsLbBackendPool

info: Executing command network lb address-pool create

+ Looking up the load balancer "pvsLb"

+ Updating load balancer "pvsLb"

data: Name : pvsLbBackendPool

data: Provisioning state : Succeeded

info: network lb address-pool create command OK
Create a load balancer rule to balance all incoming traffic on port 80 to port 80 on the addresses in the back end pool.

azure network lb rule create pvsLbRg pvsLb webLbRule -p tcp -f 80 -b 80 -t pvsFrontendPool -o pvsLbBackendPool

info: Executing command network lb rule create

+ Looking up the load balancer "pvsLb"

warn: Using default --idle-timeout 4

warn: Using default --enable-floating-ip false

warn: Using default --load-distribution Default

+ Updating load balancer "pvsLb"

data: Name : webLbRule

data: Provisioning state : Succeeded

data: Protocol : Tcp

data: Frontend port : 80

data: Backend port : 80

data: Enable floating IP : false

data: Load distribution : Default

data: Idle timeout in minutes : 4

info: network lb rule create command OK
Create a public subnet for the first NAT gateway so that it is accessible over SSH and the NNM web server port.

In this example, the public subnet is pvsPublic and has the network range 10.240.0.0/24.

azure network vnet subnet create -g pvsLbRg -e pvsVNet -n pvsPublic -a 10.240.0.0/24

info: Executing command network vnet subnet create

+ Looking up the virtual network "pvsVNet"

+ Looking up the subnet "pvsPublic"

+ Creating subnet "pvsPublic"

data: Name : pvsPublic

data: Provisioning state : Succeeded

data: Address prefix : 10.240.0.0/24

info: network vnet subnet create command OK
Create a public IP and sub domain name for the NAT gateway.

In this example, the sub domain name is exampleNatsubdomain and the public IP is pvsNatPIP.

azure network public-ip create -d exampleNatsubdomain pvsLbRg pvsNatPIP eastus

info: Executing command network public-ip create

warn: Using default --idle-timeout 4

warn: Using default --allocation-method Dynamic

warn: Using default --ip-version IPv4

+ Looking up the public ip "pvsNatPIP"

+ Creating public ip address "pvsNatPIP"

data: Name : pvsNatPIP

data: Type : Microsoft.Network/publicIPAddresses

data: Location : eastus

data: Provisioning state : Succeeded

data: Allocation method : Dynamic

data: IP version : IPv4

data: Idle timeout in minutes : 4

data: Domain name label : exampleNatsubdomain

data: FQDN : exampleNatsubdomain.eastus.cloudapp.azure.com

info: network public-ip create command OK
Create a NIC for the NAT gateway and associate it with the public IP pvsNatPIP, public subnet pvsPublic, and back end pool pvsLbBackendPool.

In this example, the new NIC is pvsNatNic.

azure network nic create --public-ip-name pvsNatPIP--subnet-name pvsPublic --subnet-vnet-name pvsVNet pvsLbRg pvsNatNic -d /subscriptions/x-x-x-x-x/resourceGroups/pvsLbRg/providers/Microsoft.Network/loadBalancers/pvsLb/backendAddressPools/pvsLbBackendPool eastus

info: Executing command network nic create

+ Looking up the network interface "pvsNatNic"

+ Looking up the subnet "pvsPublic"

+ Looking up the public ip "pvsPIP"

+ Creating network interface "pvsNatNic"

data: Name : pvsNatNic

data: Type : Microsoft.Network/networkInterfaces

data: Location : eastus

data: Provisioning state : Succeeded

data: Internal domain name suffix : gqhqyfrlprbu3jyndjoq4ap5se.bx.internal.cloudapp.net

data: Enable IP forwarding : false

data: IP configurations:

data: Name : default-ip-config

data: Provisioning state : Succeeded

data: Private IP address : 10.240.0.4

data: Private IP version : IPv4

data: Private IP allocation method : Dynamic

data:

info: network nic create command OK
Enable IP forwarding on the new interface pvsNatNic.

azure network nic set -g pvsLbRg -n pvsNatNic-f true

info: Executing command network nic set

+ Looking up the network interface "pvsNatNic"

+ Updating network interface "pvsNatNic"

data: Name : pvsNatNic

data: Type : Microsoft.Network/networkInterfaces

data: Location : eastus

data: Provisioning state : Succeeded

data: MAC address : 00-0D-3A-13-27-48

data: Internal domain name suffix : gqhqyfrlprbu3jyndjoq4ap5se.bx.internal.cloudapp.net

data: Enable IP forwarding : true

data: IP configurations:

data: Name : default-ip-config

data: Provisioning state : Succeeded

data: Private IP address : 10.240.0.4

data: Private IP version : IPv4

data: Private IP allocation method : Dynamic

data:

info: network nic set command OK
Repeat the previous steps to create a public subnet (pvsPublic2) with network range 10.240.1.0/24, create a public IP, create a NIC (pvsNatNic2) and add it to the back end pool, and enable IP forwarding on the new NIC.

Repeat this step for other NAT gateway instances that you want to use.

azure network vnet subnet create -g pvsLbRg -e pvsVNet -n pvsPublic2 -a 10.240.1.0/24

azure network public-ip create -d examplenat2subdomain pvsLbRg pvsNatPIP2 eastus

azure network nic create --public-ip-name pvsNatPIP2 --subnet-name pvsPublic2 --subnet-vnet-name pvsVNet pvsLbRg pvsNatNic2 -d subscriptions/x-x-x-x/resourceGroups/pvsLbRg/providers/Microsoft.Network/loadBalancers/pvsLb/backendAddressPools/pvsLbBackendPool eastus

azure network nic set -g pvsLbRg -n pvsNatNic2 -f true
Create a security group for the NAT gateways.

In this example, the security group is pvsPublicNSG.

azure network nsg create pvsLbRg pvsPublicNSG eastus

info: Executing command network nsg create

+ Looking up the network security group "pvsPublicNSG"

+ Creating a network security group "pvsPublicNSG"

data: Name : pvsPublicNSG

data: Type : Microsoft.Network/networkSecurityGroups

data: Location : eastus

data: Provisioning state : Succeeded

data: Security rules:

data: Name Source IP Source Port Destination IP Destination Port Protocol Direction Access Priority

data: ----------------------------- ----------------- ----------- -------------- ---------------- -------- --------- ------ --------

data: AllowVnetInBound VirtualNetwork * VirtualNetwork * * Inbound Allow 65000

data: AllowAzureLoadBalancerInBound AzureLoadBalancer * * * * Inbound Allow 65001

data: DenyAllInBound * * * * * Inbound Deny 65500

data: AllowVnetOutBound VirtualNetwork * VirtualNetwork * * Outbound Allow 65000

data: AllowInternetOutBound * * Internet * * Outbound Allow 65001

data: DenyAllOutBound * * * * * Outbound Deny 65500

info: network nsg create command OK
Create a rule in the pvsPublicNSG to allow SSH to the NAT gateway.

In this example, the new rule is called SSHRule and the rule has a priority of 1000. This gives it precedence over the existing rules seen in the previous step.

azure network nsg rule create --protocol tcp --direction inbound --priority 1000 --destination-port-range 22 --access allow pvsLbRg pvsPublicNSG SSHRule

info: Executing command network nsg rule create

warn: Using default --source-port-range *

warn: Using default --source-address-prefix *

warn: Using default --destination-address-prefix *

+ Looking up the network security group "pvsPublicNSG"

+ Looking up the network security rule "SSHRule"

+ Creating a network security rule "SSHRule"

data: Name : SSHRule

data: Type : Microsoft.Network/networkSecurityGroups/securityRules

data: Provisioning state : Succeeded

data: Source IP : *

data: Source Port : *

data: Destination IP : *

data: Destination Port : 22

data: Protocol : Tcp

data: Direction : Inbound

data: Access : Allow

data: Priority : 1000

info: network nsg rule create command OK
Create a rule in the pvsPublicNSG to allow all traffic to the NAT gateway from within the virtual network.

In this example, the new rule is called PrivateToPublicRule and the rule has a priority of 1001. This gives it precedence over the existing rules that disallow traffic.

azure network nsg rule create --direction inbound --priority 1001 --source-address-prefix VirtualNetwork --destination-port-range 0-65535 --access allow pvsLbRg pvsPublicNSG PrivateToPublicRule

info: Executing command network nsg rule create

warn: Using default --protocol *

warn: Using default --source-port-range *

warn: Using default --destination-address-prefix *

+ Looking up the network security group "pvsPublicNSG"

+ Looking up the network security rule "PrivateToPublicRule"

+ Creating a network security rule "PrivateToPublicRule"

data: Name : PrivateToPublicRule

data: Type : Microsoft.Network/networkSecurityGroups/securityRules

data: Provisioning state : Succeeded

data: Source IP : VirtualNetwork

data: Source Port : *

data: Destination IP : *

data: Destination Port : 0-65535

data: Protocol : *

data: Direction : Inbound

data: Access : Allow

data: Priority : 1001

info: network nsg rule create command OK
Create a rule in the pvsPublicNSG to allow traffic to the NNM webserver from the Internet. The default port is 8835.

In this example, the new rule is called PVSWebRule and the rule has a priority of 1002. This gives it precedence over the existing rules that disallow traffic.

azure network nsg rule create --direction inbound --priority 1002 --protocol tcp --source-address-prefix Internet --destination-port-range 8835 --access allow pvsLbRg pvsPublicNSG PvsWebRule

info: Executing command network nsg rule create

warn: Using default --source-port-range *

warn: Using default --destination-address-prefix *

+ Looking up the network security group "pvsPublicNSG"

+ Looking up the network security rule "PvsWebRule"

+ Creating a network security rule "PvsWebRule"

data: Name : PvsWebRule

data: Type : Microsoft.Network/networkSecurityGroups/securityRules

data: Provisioning state : Succeeded

data: Source IP : Internet

data: Source Port : *

data: Destination IP : *

data: Destination Port : 8835

data: Protocol : Tcp

data: Direction : Inbound

data: Access : Allow

data: Priority : 1002

info: network nsg rule create command OK
Create a rule in the pvsPublicNSG to allow HTTP traffic to the NAT gateway so it can be forwarded to the web servers being load balanced.

In this example, the new rule is called AllWebRule and the rule has a priority of 1003. This gives it precedence over the existing rules that disallow traffic.

azure network nsg rule create --direction inbound --priority 1003 --protocol tcp --source-address-prefix Internet --destination-port-range 80 --access allow pvsLbRg pvsPublicNSG AllWebRule
Assign the security group pvsPublicNSG to the pvsNatNic, which will be used as the interface of the NAT gateway when it is launched.

azure network nic set -g pvsLbRg -n pvsNatNic -o pvsPublicNSG

info: Executing command network nic set

+ Looking up the network interface "pvsNatNic"

+ Looking up the network security group "pvsPublicNSG"

+ Updating network interface "pvsNatNic"

data: Name : pvsNatNic

data: Type : Microsoft.Network/networkInterfaces

data: Location : eastus

data: Provisioning state : Succeeded

data: Internal domain name suffix : gqhqyfrlprbu3jyndjoq4ap5se.bx.internal.cloudapp.net

data: Enable IP forwarding : false

data: IP configurations:

data: Name : default-ip-config

data: Provisioning state : Succeeded

data: Private IP address : 10.240.0.4

data: Private IP version : IPv4

data: Private IP allocation method : Dynamic

data:

info: network nic set command OK
Repeat the previous step for any other NAT gateway NICs you have created.

azure network nic set -g pvsLbRg -n pvsNatNic2 -o pvsPublicNSG
Create an availability set for all the VM instances that will be created. This is required for having more than one VM attached to the load balancer.

azure availset create pvsLbRg pvsLbAs eastus

info: Executing command availset create

+ Looking up the availability set "pvsLbAs"

+ Creating availability set "pvsLbAs"

info: availset create command OK
Launch the NAT gateway instance. In this example CentOS 7 is used.

In this example, the SSH key azurePVS_id_rsa.pub is used. If you do not have an SSH key, refer to the Azure documentation for instructions on how to generate a key.

Note: If you select a different image to install on your NAT gateway virtual machine, ensure that it is a platform that NNM supports.

azure vm create --resource-group pvsLbRg --name pvsNatGateway --location eastus --os-type linux --nic-name pvsNatNic --vnet-name pvsVNet --vnet-subnet-name pvsPublic --storage-account-name pvslbstore --image-urn CentOS -r pvsLbAs --ssh-publickey-file ~/.ssh/azurePVS_id_rsa.pub --admin-username centos

info: Executing command vm create

+ Looking up the VM "pvsNatGateway"

info: Verifying the public key SSH file: ~/.ssh/azurePVS_id_rsa.pub

info: Using the VM Size "Standard_DS1"

info: The [OS, Data] Disk or image configuration requires storage account

+ Looking up the storage account pvsstore

+ Looking up the NIC "pvsNatNic"

info: Found an existing NIC "pvsNatNic"

info: The storage URI 'https://pvslbstore.blob.core.windows.net/' will be used for boot diagnostics settings, and it can be overwritten by the parameter input of '--boot-diagnostics-storage-uri'.

+ Creating VM "pvsNatGateway"

info: vm create command OK
Launch any other NAT gateway instances.

azure vm create --resource-group pvsLbRg --name pvsNatGateway2 --location eastus --os-type linux --nic-name pvsNatNic2 --vnet-name pvsVNet --vnet-subnet-name pvsPublic2 --storage-account-name pvslbstore --image-urn CentOS -r pvsLbAs --ssh-publickey-file ~/.ssh/azurePVS_id_rsa.pub --admin-username centos
Create a private subnet for the instances that won't have a public IP address.

In this example, the private subnet is pvsPrivate.

azure network vnet subnet create -g pvsLbRg -e pvsVNet -n pvsPrivate -a 10.240.2.0/24

info: Executing command network vnet subnet create

+ Looking up the virtual network "pvsVNet"

+ Looking up the subnet "pvsPrivate"

+ Creating subnet "pvsPrivate"

data: Name : pvsPrivate

data: Provisioning state : Succeeded

data: Address prefix : 10.240.2.0/24

info: network vnet subnet create command OK
Create a route table for the private subnet.

In this example, the route table is pvsPrivateUDR.

azure network route-table create -g pvsLbRg -n pvsPrivateUDR -l eastus

info: Executing command network route-table create

+ Looking up Route Table "pvsPrivateUDR"

+ Creating Route Table "pvsPrivateUDR"

data: Name : pvsPrivateUDR

data: Type : Microsoft.Network/routeTables

data: Location : eastus

data: Provisioning state : Succeeded

info: network route-table create command OK
Create a route to the internet using the NAT gateway as the next hop for instances in the private subnet.

In this example, the private IP address of the NAT gateway is 10.240.0.4.

azure network route-table route create -g pvsLbRg -r pvsPrivateUDR -n RouteToInternet -a 0.0.0.0/0 -y VirtualAppliance -p 10.240.0.4

info: Executing command network route-table route create

+ Looking up Route Table "pvsPrivateUDR"

+ Looking up route "RouteToInternet" in route table "pvsPrivateUDR"

+ Creating route "RouteToInternet" in a route table "pvsPrivateUDR"

data: Name : RouteToInternet

data: Provisioning state : Succeeded

data: Next hop type : VirtualAppliance

data: Next hop IP address : 10.240.0.4

data: Address prefix : 0.0.0.0/0

info: network route-table route create command OK
Associate the route table pvsPrivateUDR with the private subnet pvsPrivate.

azure network vnet subnet set -g pvsLbRg -e pvsVNet -n pvsPrivate -r pvsPrivateUDR

info: Executing command network vnet subnet set

+ Looking up the virtual network "pvsVNet"

+ Looking up the subnet "pvsPrivate"

+ Looking up Route Table "pvsPrivateUDR"

+ Updating subnet "pvsPrivate"

data: Name : pvsPrivate

data: Provisioning state : Succeeded

data: Address prefix : 10.240.2.0/24

info: network vnet subnet set command OK
Create a NIC for an example instance in the private subnet. You will need to create a new NIC for every additional instance you create.

In this example, the new NIC is named pvsPrivateNic.

azure network nic create --subnet-name pvsPrivate --subnet-vnet-name pvsVNet pvsLbRg pvsPrivateNic eastus

info: Executing command network nic create

+ Looking up the network interface "pvsPrivateNic"

+ Looking up the subnet "pvsPrivate"

+ Creating network interface "pvsPrivateNic"

data: Name : pvsPrivateNic

data: Type : Microsoft.Network/networkInterfaces

data: Location : eastus

data: Provisioning state : Succeeded

data: Internal domain name suffix : gqhqyfrlprbu3jyndjoq4ap5se.bx.internal.cloudapp.net

data: Enable IP forwarding : false

data: IP configurations:

data: Name : default-ip-config

data: Provisioning state : Succeeded

data: Private IP address : 10.240.2.4

data: Private IP version : IPv4

data: Private IP allocation method : Dynamic

data:

info: network nic create command OK
Launch an example instance into the private subnet pvsPrivate using the pvsPrivateNic as the NIC.

azure vm create --resource-group pvsLbRg --name exampleInstance --location eastus --os-type linux --nic-name pvsPrivateNic --vnet-name pvsVNet --vnet-subnet-name pvsPrivate --storage-account-name pvslbstore --image-urn CentOS --ssh-publickey-file ~/.ssh/azurePVS_id_rsa.pub --admin-username centos

info: Executing command vm create

+ Looking up the VM "exampleInstance"

info: Verifying the public key SSH file: ~/.ssh/azurePVS_id_rsa.pub

info: Using the VM Size "Standard_DS1"

info: The [OS, Data] Disk or image configuration requires storage account

+ Looking up the storage account pvsstore

+ Looking up the NIC "pvsPrivateNic"

info: Found an existing NIC "pvsPrivateNic"

info: This is an NIC without publicIP configured

info: The storage URI 'https://pvsstore.blob.core.windows.net/' will be used for boot diagnostics settings, and it can be overwritten by the parameter input of '--boot-diagnostics-storage-uri'.

+ Creating VM "exampleInstance"

info: vm create command OK
Repeat the previous steps to create any additional private instances if they are going into a new subnet. To create a new instance in an existing subnet, simply repeat the launch into the subnet step.

azure network vnet subnet create -g pvsLbRg -e pvsVNet -n pvsPrivate2 -a 10.240.3.0/24

azure network route-table create -g pvsLbRg -n pvsPrivateUDR2 -l eastus

azure network route-table route create -g pvsLbRg -r pvsPrivateUDR2 -n RouteToInternet -a 0.0.0.0/0 -y VirtualAppliance -p 10.240.1.4

azure network vnet subnet set -g pvsLbRg -e pvsVNet -n pvsPrivate2 -r pvsPrivateUDR2

azure network nic create --subnet-name pvsPrivate2 --subnet-vnet-name pvsVNet pvsLbRg pvsPrivateNic2 eastus

azure vm create --resource-group pvsLbRg --name exampleInstance2 --location eastus --os-type linux --nic-name pvsPrivateNic2 --vnet-name pvsVNet --vnet-subnet-name pvsPrivate2 --storage-account-name pvslbstore --image-urn CentOS --ssh-publickey-file ~/.ssh/azurePVS_id_rsa.pub --admin-username centos
Connect to the new NAT gateway instances using the public DNS name that was created when your public IP was created.

ssh -i ~/.ssh/azurePVS_id_rsa.pub [email protected]
Once logged in, configure iptables and IP forwarding.

sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

sudo iptables -t nat -A PREROUTING -i eth0 ! -s 10.240.0.0/16 -p tcp --dport 80 -j DNAT --to-destination 10.240.2.4:80

The first sudo command tells the kernel to allow IP forwarding. The second sudo command masquerades packets received from internal instances as if they originated from the NAT gateway instance. The last command enables port forwarding so traffic to the NAT gateway on port 80 gets forwarded to port 80 on 10.240.2.4. In this example 10.240.2.4 is one the web servers being load balanced.

Tip: Consider saving these commands in a startup script, because these settings will not persist if the instance is rebooted.