I am just wondering how two existing VPC with having their setup with common CIDR range 10.0.0.0/16, and if requirement comes for peering how we can handle that as overlapping CIDRs are not allowed.
Related
I am a beginner with azure vnet peering, so please indulge me if this is such an obvious question.
I would like to vnet peer one vnet to multiple vnets. All those vnets however uses the same address space. Let me explain more with examples.
Let's say vnet_source is the one that will peer with some existing vnets.
vnet_source > 192.168.0.0/16 for example
vnet1> 10.0.0.0/16
vnet2> 10.0.0.0/16
vnet3> 10.0.0.0/16
Would this be possible? For one vnet (vnet_source) to peer with other vnets that are using the same address space, in this case (vnet 1,2, and 3)?
and if so is there a routing trick that can identify, that in this case 10.0.1.81 for example ip address belongs to vnet1 and not.
Any help would be highly appreciated!
Thank you so much.
I am still in the planning phase, so have not tested yet.
Unfortunately it is not possible to implement vnet peering between vnets with same address space.
There are likely to be address conflicts (same IP address used in both locations) and
Azure Route tables won't be able to decide where to send the traffic.(VM with IP 10.0.0.10 from vnet1, vnet2 or vnet3?)
https://community.cisco.com/t5/other-collaboration-subjects/the-best-way-to-connect-2-lan-s-with-the-same-ip-addresses/td-p/2724403
It is important to use unique IP address spaces for each virtual network used in Azure so that routing can occur between virtual networks.
If virtual networks have the same IP address space it would not be possible to route traffic between resources from different vnets.
https://superuser.com/questions/1661852/can-two-networks-connected-to-a-router-both-have-a-host-with-the-same-ip-address
L2 forwarding can solve this problem but Azure does not support it for peering.
https://blog.ipspace.net/2019/11/stretched-layer-2-subnets-in-azure.html
Any ideas on a workaround on how to peer 2 vnet in azure where one of the vnet has a existing peering with a vnet that has an overlapping cidr range?
Looking at NAT gateways but this seems more for routing traffic from a private out to the internet.
Thanks
Brian
It's not possible to peer virtual networks with overlapping address space. If you intend to peer these VNets, you need to change the address space in one of that VNets.
VNet peering enables you to seamlessly connect Azure virtual networks. Once peered, the VNets appear as one, for connectivity purposes. If there are overlapping CIDR ranges, the address conflicts.
If you have a NSG at the Subnet level, will it be applied between VMs that resides in the same subnet?
Yes, it does apply to VMs within the same subnet. As per NSG documentation:
It's important to note that security rules in an NSG associated to a subnet can affect connectivity between VM's within it.
Let's take the following scenario:
I have a resource group in the East Region with 1 VM
I have a resource group in the West Region with 1 VM
Both of these VMs are only accessible via Private IP addresses. RDP via Public IP address is not an option. One would assume that in order for me to RDP to these machines, I would have to VPN into Azure's gateway first. However, I don't want to create a virtual gateway in every single resource group.
Is it possible for me to vpn into one resource (in one resource group), and access all of the machines in all other resource groups?
Yes, It's possible to do this with VNet peering(connecting VNets within the same Azure region). You could follow this to implement a hub-spoke network topology in Azure. In this case, the hub VNet is a peering VNet with allow gateway transit enabled and the spoke VNet is a peering VNet with use remote gateways enabled.
please note that you cannot use remote gateways or allow gateway transit with global peering(connecting VNets across Azure regions). Refer to requirements and constraints about global peering.
To use remote gateways or allow gateway transit, peered virtual
networks in must be in the same region.
so you have to move the peering VNets in the same region if the two VNets in each resource group are not in the same region.
Another option will create a separate VPN gateway in another resource group but this is not your expectation. Note that
A Point-to-Site client can only connect to resources in the VNet in
which the virtual network gateway resides.
Refer to VPN gateway FAQ.
You can use vnet peering with Use remote gateways checkbox enabled. You need to peer the vnets together and check use remote gateways on the second vnet (one without gateway).
Reading:
https://learn.microsoft.com/en-us/azure/architecture/reference-architectures/hybrid-networking/hub-spoke
https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview
This question is for AWS Engineers. I was reading about AWS VPC. It says VPC peering allows to connect 1 subnet to another subnet inside another VPC. Also it says, Instances on both subnet work as if they were in 1 subnet. So the question comes, "what happens if the IPs on both instances were identical?" Are they going to conflict? If not, how can I distinguish which one is which?
Thank you
This is an inaccurate description.
From VPC Peering:
A VPC peering connection is a networking connection between two VPCs that enables you to route traffic between them privately. Instances in either VPC can communicate with each other as if they are within the same network. You can create a VPC peering connection between your own VPCs, with a VPC in another AWS account, or with a VPC in a different AWS Region.
VPC Peering is a connection between two VPCs (not two Subnets). One of the rules for VPC peering is that the IP address ranges of the two VPCs cannot overlap. Thus, the situation described in the question cannot eventuate.
From Invalid VPC Peering Connection Configurations:
You cannot create a VPC peering connection between VPCs with matching or overlapping IPv4 CIDR blocks.
If the VPCs have multiple IPv4 CIDR blocks, you cannot create a VPC peering connection if any of the CIDR blocks overlap (regardless of whether you intend to use the VPC peering connection for communication between the non-overlapping CIDR blocks only).
Once a VPC Peering connection is established, the Route Tables need to be modified to route traffic across the VPC Peering connection. It is possible to modify only the route tables for a specific subnet, so this could be considered to be peering just a single subnet, but it would need to be specifically configured this way. (It is actually a common use-case, so that only a single subnet in each VPC is peered, acting as a type of DMZ for added security.)