Can someone explain to me what actually happens in the back-end to the load balancer (v2) for the two scenarios:
Applying Inbound NAT rules.
Applying Load Balancing Rules.
You would use NAT rule when you have 1 backend server or you know which backend server to get to and loadbalancing rule when you want to loadbalance to multiple backend servers.
NAT rule must be explicitly attached to a VM (or network interface) to complete the path to the target; whereas Load Balancing rule need not be. In the latter case, a VM is selected (from the back-end address pool or VMs) to complete the path to the target.
Please note that "Load balancing rule" used to distribute the traffic to available backend VMs while "Inbound nat rule" used to forward the traffic to a specific VM.
For example, assume your front end IP is 10.10.10.4 while you have three VMs in the backend pool which is having IP's of 10.10.10.5, 10.10.10.6, 10.10.10.7 respectively.
If you want to distribute the traffic which hits your frontend IP to all the three backend VMs, you will use "load balancing rule" option.
If you want to forward the traffic which hits your frontend IP to a specific VM 10.10.10.5 then you will use "inbound nat rule" option.
So in simple words,
Load balancing rule - Distributes,
Inbound nat rule - Forwards
this documentation link will help: https://learn.microsoft.com/en-us/azure/load-balancer/components#inbound-nat-rules
We added examples to help clarify. You can think of inbound NAT rules as a special type of Load Balancing rules to reference specific VMs.
-- Anavi N
Senior PM load, Azure Load Balancer
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I am currently trying to learn azure cloud, I have worked with AWS before so may be trying to carry over some concepts here.
I need to know how we can configure a logical firewall to allow traffic from an azure load balancer to and VMs(scale sets or backend pools)?
I was able to do this between different VMs by assigning the VMs to different application security groups and allowing respective traffic from those groups in the network security group. I found the service tag 'AzureLoadBalancer' as an option in NSG rules but it seems that is only for allowing traffic from healthprobes and not from actual load balancer (also there is no option to select a certain load balancer). In the end I had to allow traffic from the public ip of the load balancer to the VNET to get the load balancer to work.
I hope there is a logical way to do this and if there is I am not sure what I am missing here, would appreciate anyone who could help here.
Normally you wouldn't want to firewall traffic from the Azure Load Balancer as it's a load balancer so it needs to be able to reach your endpoints. I'm not quite sure on what you are trying to achieve here. You might be able to simply micro-segment your endpoints on different subnets and apply different NSGs (with different allow/deny rules) on the subnet level. Otherwise an actual firewall would be required between your Azure Load Balancer and endpoints if you need L7 inspection for example.
Could you help me with understanding the pricing for loadbalancer in Azure. Here what I've found in manual https://azure.microsoft.com/en-us/pricing/details/load-balancer/
Am I right, if I add several Frontend IP configurations, Backend pools and Inbound NAT rules only, without any Load balancing rules I'll be charged only for the amount of data processed? The reason I am asking is that I can't find what is "outbound rules" there is no such item in the settings.
And,in general, my aim is just to redirect ports from public IP to VM.
Yes, you are right. If you are creating only Inbound NAT rules, you will be charged only for the amount of data processed and the charge of the Public IP address resource which is attached to the LB.
Outbound rules are not visible in Portal. You can configure it via CLI or PowerShell. It is used in scenarios where you have VMs without Public IP which are part of Internal Load balancers and need to talk to Internet.
Please forgive my ignorance.
Question:
How can I control network traffic to a publicIP resource and send it to multiple different resources based on destination port?
Background:
I have setup some VMs that are configured with only private IPs in different subnets. All belong to the same Virtual Network. All these VMs have different services and I do not want HA as I do not need it and it costs money.
I just want all the services on these VMs to communicate out using the same single publicIP and I want to split incoming traffic to that same publicIP between my resources based on destination port.
Seems like a straight forward requirement right?
At first I though "this must be a task for the Load Balancer service" as it's operating at L4 and tried to set it up but I was not able to split inbound traffic on different ports to more than a single VM or a single availability set. I do not understand why you can only use Load Balancers NAT rules with a single VM or Availability Set.
I can probably delete/re-create all VMs (thank you Microsoft..) into a single availability set that only has 1 fault and 1 error domain but does this make any sense?
It just seems to me like a dirty workaround using availability sets in a way they are not meant to in order to solve a very basic thing.
Thanks!
Basically, you could create a public-facing Azure Load balancer then target the VMs or Availability Sets to the backend pools of this load balancer. What you need to do is to configure the load balancing rules and some health probes or inbound NAT rules for the backend services with ports forwarding.
Refer to the SO answer.
You would use NAT rule when you have 1 backend server or you know
which backend server to get to and load balancing rules when you want
to load-balance to multiple backend servers.
NAT rule must be explicitly attached to a VM (or network interface) to
complete the path to the target; whereas Load Balancing rule need not
be. In the latter case, a VM is selected (from the back-end address
pool or VMs) to complete the path to the target.
Additionally, Azure Load balancer supports two SKUs: basic and standard. Different SKUs support different backend pool endpoints. Read more details about Load Balancer SKU comparison.
I have setup a few VM's and a load balancer so that we can have one outgoing IP. Right now i am having issues to connect to the internet from inside my VM. If i open internet explorer and try to access a website, it shows waiting for reply and then "This page can’t be displayed".
Each VM is connected to the same subnet.
The subnet has a NSG attached to it and each VM is part of the subnet.
NSG attached to the subnet.
There is then a load balancer to allow incoming RDP but with different ports to the different VM's.
I think i am missing the SNAT but i have no idea where to configure that. From what i have read, i am using level 2 "Public Load Balancer associated with a VM (no Instance Level Public IP address on the instance)". Multiple VM's on a subnet and one load balancer to share one IP address.
Where do i actually go to set up the SNAT? Or is there another issue i am missing here?
Probably, you could add the load balancing rules for TCP port 80 or 443 instead of inbound NAT rules. NAT rules always use for port forwarding. Moreover, you do not need add NAT rules for DNS. This works on my side.
A load balancer rule defines how traffic is distributed to the VMs. The rule defines the front-end IP configuration for incoming traffic, the back-end IP pool to receive the traffic, and the required source and destination ports.
I've got multiple questions on the setup of a gateway and VM, so here is what I have actually.
I've got an Application Gateway, and two VM Ubuntu, everything hosted on Azure. They are all on the same Virtual Network. Both VM have only a private IP (10.1.0.4 and 10.1.0.5) and the Gateway have a private IP (10.1.1.4) and a public IP. Because only the Gateway have a public IP, I guess that everything have to go through it, and this is what I want to.
The goals I try to achieve :
Make a load balancer on the port 1680, redirected to port 1680.
To redirect the SSH of each VM to connect specifically to one because at the moment, they have no public IP. Is it possible to do this with a path based rule ? Like www.example.com/VM1 to connect by SSH to the first VM ? If no, what can be used to differentiate the SSH connection of the VM1 and of the VM2 ?
To redirect the port 80 of the gateway to the port 8080 of a specific VM. As my previous example, www.example.com/adminPanelVM1 to connect to the first VM on port 80 (redirected to port 8080 on the VM)
I already managed to create the redirection of the port 1680 of the Gateway with an HTTP Parameter, a Listener and a Rule.
Azure Application Gateway
The Azure Application Gateway operates at the layer 7 in the OSI model on the HTTP/HTTPS/WebSocket protocols, because of that any other protocol (like SSH), is not possible to route.
You got a few options tho.
You can use a Network Security Group, or NSG, for access control to your virtual machines. In the NSG you define where the traffic can come from that is allowed access to the VMs.
A NSG behaves like a access-control-list filtering traffic based on source and destination information and evaluating rules in order of priority. See this page for more information about NSGs.
Another option is to use a load balancer.
Azure Load Balancer
If you need to do port mapping, like you describe in your question, then a simple load balancer might be a better solution for you. An Azure Load Balancer works at a lower level in the in the OSI model, namely layer 4 (transport layer), handling TCP/UDP traffic.
So, if you are using a load balancer, then you can set up NAT rules to forward your traffic to specific machines, in other words, if you want to do:
LB port 1234 redirects to VM1 port 22 and
LB port 4312 redirects to VM2 port 22
you can do that using PowerShell as described in the Creating a public load balancer in Resource Manager by using PowerShell article.
There are quite a few steps but it walks you through the whole process of creating NAT rules, NICs and associated virtual machines.
Azure Application Gateway vs Azure Load Balancer?
These two cervices are distinctly different services and are trying to solve different problem, although those problems might look similar :)
The primary uses of an Application Gateway are:
SSL termination
cookie-based session affinity
round robin for load balancing traffic
Where as the Azure Load Balancer service works as the TCP/UDP level and support e.g. port mapping.
Cost wise, the load balancer service is free while the application gateway is billed per hour.
There are many great articles on this topic, when to pick which service. See for example the links for more details
When to use Azure Load Balancer or Application Gateway
Frequently asked questions for Application Gateway