Wsrtjtyk

I'm trying to create a load balancer to sit in front of my two web machines although I'm confused by this screen (see attached). I'm not sure what to enter into the "Public IP address" field? If it's the IP then where do I get the value from?

Many thanks

Azure load balancer wizard

If you create a public type of load balancer, you need create a new public IP address or use existing public IP address so that you can access the backend virtual machines via the public facing IP address as the frontend configuration. Here you just need to name a public IP such as Load balancer-pip and enter into the "Public IP address" field.

Besides, if you want to add the two individual machines (not in an availability set or a scale set) as the backend pool, you need to create a Standard SKU of load balancer since Standard LB is fully integrated with a virtual network, you can put any virtual machine (with standard SKU public ip or without public IP)in a single virtual network as the backend pool endpoint, while the basic load balancer only support a single virtual machine or Virtual machines in a single availability set or virtual machine scale set.

If the two web machines are in an existing availability set or a scale set, you can select the Basic SKU load balancer.

For more information, you can see Azure Load balancer.

Taking a look at the screenshot provided there. You are on a free trial & are experimenting with the Azure Load Balancer.

We have 2 SKU's:
Basic
Standard

Since you are looking for an ELB (External/public Load Balancer) should you choose to use a standard. Then, the public IP as well as the backend VM's need to have a standard IP's.

Thus, I would suggest the following:
Note: Assuming that you have not exhausted the 5 free public Ip's that you get from Azure.

Step 1: Deploy your webservers into an "Availability Set"
Step 2: Deploy the basic SKU eternal load balancer with a public IP address
Preferred to make it static.
Step 3: Create load balancing rules as required over necessary ports for which your website is bound (443/80)
- You may also choose to have a PAT done (Port Address Translation)
- You can also test between affinity/tupples which provide sticky sessions in the order of client IP > Client IP & Protocol > Default/5tuple
Step 4: Finally add the backend pool

Troubleshooting further:
Once you have reached this point, it's safe to say you have got the configuration right!
But, check the following
1. Check for NSG at the subnet level as well as the VM nic Level
2. make sure you have allowed the Azure load balancer default rule
3. Switch the probe protocol from HTTP to TCP if you application anticipates a 3-way handshake and an acknowledgment. (layer 3-4)
4. VM with Public IPs:
If your VM/VMs has a public IP's then keyNote the traffic outbound would take the respective public IP. Should you want the traffic to take the Load Balancer IP for SNAT. Then, kindly remove the public IP that is set on the VM/VM's.

Effective testing:
Browse your application by creating custom landing pages from a private window of a browser. Say ex;
I hit VM1 - text over html header
I hit VM2 - text over html header

Should you have got this working, you are good to move your test workloads and applications on to these servers.

Advanced Troubleshooting:
- Here on the load balancer takes no blame as it's working as expected.
- You would want to check the ports on the application servers
- Public IP Time out: https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-tcp-idle-timeout

Commands:
Windows CMD:

Netstat -ano | Findstr port#
//replace port with the respective port number

Linux:
$ netstat -tulpn | grep port#
//replace port with the respective port number

Make sure that they are listening.

• If you have a Linux machine. Make sure that your Ip tables are not blocking any custom ports that you may be using

I hope this helps.

Reference Documents:
https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-troubleshoot
https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-distribution-mode