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Communication between two Azure virtual networks

Anonymous
2022-11-01T13:32:08.663+00:00

Hi,

I have attached here the snap taken from the link below:256028-azure-vnets.png

https://learn.microsoft.com/en-us/azure/architecture/reference-architectures/hybrid-networking/vnet-peering

The highlighted sentence confused me. I understand that because of the default inbound security rule "AllowVNetInBound", VM's in two separate virtual networks be able to communicate with each other via their respective public addresses. Please correct me otherwise.

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
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  1. Alan Kinane 16,951 Reputation points MVP Volunteer Moderator
    2022-11-01T13:45:58.233+00:00

    Virtual Networks are isolated from each other by default unless you connect them (usually by using VNET Peering), this allows those resources to communicate via their private IP addresses. The AllowVnetInBound rule is pre-configured to allow traffic within any connected VNETs, note the source and destination on this rule are both VirtualNetwork.

    If the VNETs are not connected then you use public IP addresses instead but you would need to add an Inbound access rule to your network security group as this traffic is denied by default due to the pre-configured DenyAllInBound rule which has a source and destination of Any.

    1 person found this answer helpful.

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  1. Michael Durkan 12,241 Reputation points MVP
    2022-11-01T13:48:28.23+00:00

    Hi

    this is where VNET Peering comes in. You need to create peering between the 2 Virtual Networks in order for them to communicate with each other.

    As the statement says, each Virtual Network is an isolated portion of the Azure Public network. You need to create peering so that the resources behind each NSG in each VNET can communicate with each other across the Azure Backbone network using their private IP Addresses.

    Check the link here for more details:

    https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview

    Thanks

    Michael Durkan

    • If the reply was helpful please upvote and/or accept as answer as this helps others in the community with similar questions. Thanks!
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  2. Preetha Rajesh 126 Reputation points
    2022-11-01T14:47:15.803+00:00

    Hi @MohammedShaifal-2799

    The default inbound security rule “AllowVNetInbound” will not allow VMs in two separate virtual network to communicate with each other. You need to enable additional capabilities as mentioned in the below link

    https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview#:~:text=When%20a%20subnet%20is%20created,other%20route%2C%20to%20the%20Internet.

    AllowVnetinbound rule permits all the hosts inside the virtual network to communicate with each other.

    The above article will help you to get more insights on basic concepts of networking.

    Thank You!

    Regards
    Preetha

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