An Azure virtual network (VNet) provides connectivity and security for virtual machines and allows access to the public internet and other VMs. Network security groups contain rules that allow or deny network traffic, and Azure load balancers distribute incoming internet traffic across VMs. Availability sets distribute VMs across update and fault domains for redundancy and high availability. Virtual network gateways connect Azure VNets and on-premises networks, while Traffic Manager controls traffic distribution across endpoints in different datacenters.

1. AZURE NETWORKING
BASICS
By Sai Kishore

2. WHAT ISVIRTUAL NETWORK IN AZURE?
An Azure virtual network (VNet) is a representation of your own network
in the cloud.
Connectivity.
Access to the public Internet.
Access toVMs.
Security.
 AzureVirtual Network Contains
 Ipaddress - Public and Private.
 Subnet - Subnet is a range of IP
addresses in theVnet.

3. NETWORK SECURITY GROUP
Network security group (NSG) contains a list of Access Control List (ACL) rules
that allow or deny network traffic to yourVM instances in aVirtual Network. NSGs
can be associated with either subnets or individualVM instances within that
subnet.
Reference Link - https://azure.microsoft.com/en-in/documentation/articles/virtual-networks-create-nsg-arm-
pportal/?cdn=disable

4. AZURE LOAD BALANCER
Virtual machines and cloud services in aVirtual network can
be exposed to Internet using Azure Load balancers.
You can use an load balancer to provide high availability and
network performance to your applications.
 Load balance incoming Internet traffic to virtual machines.
 Load balance traffic between virtual machines in a virtual
network, between virtual machines in cloud services, or between
on-premises computers
 Forward external traffic to a specific virtual machine.
 Azure Load Balancer uses a hash-based distribution algorithm
 Reference Link - https://azure.microsoft.com/en-
in/documentation/articles/load-balancer-overview/

5. AVAILABILITY SETS -
MicrosoftAzure platform events that can affect the availability of your virtual machines: planned
maintenance and unplanned maintenance.
 Planned maintenance events are periodic updates made by Microsoft to the underlying Azure platform to improve overall reliability,
performance, and security of the platform infrastructure.
 Unplanned maintenance events occur when the hardware or physical infrastructure underlying your virtual machine has faulted in some
way.This may include local network failures, local disk failures, or other rack level failures. When such a failure is detected, the Azure
platform will automatically migrate your virtual machine from the unhealthy physical machine hosting your virtual machine to a healthy
physical machine.
Follow best practices when you design your application for high availability
 To reduce the impact of downtime due to one or more of these events, we recommend the following high availability best practices for your
virtual machines:
 Configure multiple virtual machines in an availability set for redundancy , even for applications
 Combine the Load Balancer with availability sets.

6. UPDATE AND FAULT DOMAINS -
Fault Domain (FD) – A fault domain is a
grouping of hardware (rack of resources like
servers, power etc.) in whichVirtual
Machines are arranged. By default, the
virtual machines configured within your
availability set are separated across up to 3
fault domains for resource manager
deployments.
Update Domain (UD) – An update Domain on the other hand is an arrangement within the Racks so as to provide the
Web or worker role instances with high availability by ensuring that only one of Instances of the roles will be down for
update at one time. For a given availability set, 5 update domains are assigned by default.
Each virtual machine in your availability set is assigned an update domain and a fault domain by the underlyingAzure
platform.

7. VIRTUAL NETWORK GATEWAY
 A virtual network gateway is used to send network traffic
between Azure virtual networks and on-premises locations and
also between virtual networks within Azure (VNet-to-VNet).
VPN and Express Route
VPN – Site to Site, Point to Site &Vnet toVnet Connectivity.
Basic, Standard & High Performance
 Reference Link - https://azure.microsoft.com/en-
in/documentation/articles/vpn-gateway-about-vpngateways/

8. TRAFFIC MANAGER IN AZURE
Microsoft AzureTraffic Manager allows you to control the distribution of user
traffic for service endpoints in different datacenters. Service endpoints supported
byTraffic Manager include AzureVMs,Web Apps, and cloud services.
Traffic Manager uses the Domain Name System (DNS)
Traffic Manager benefits
 Improve availability of critical applications
 Improve responsiveness for high-performance applications
 Perform service maintenance without downtime
 Combine on-premises and Cloud-based applications