In Azure, I have 2 VMs, each in their own subnet (see image below). To my surprise, both VMs can "see" each other (using ping).
The subnet address ranges are:
net1-subnet1: 10.0.1.0/24
net1-subnet2: 10.0.2.0/24
The VMs (NIC) IPs are:
vm1: 10.0.1.4
vm2: 10.0.2.4
This is the setup
Why are both VMs able to ping each other? I thought since they are in different subnets, they would not be able to "see" each other. Is this an Azure specific feature?
Thanks
Azure routes traffic between subnets in the same virtual network (or peered virtual networks) by default as described in the Azure virtual networks overview.
You can use network security groups to filter traffic flowing in- and outbound to/from these subnets. The default rules will allow traffic from a virtual network, so you will have to add some of your own rules with a higher priority to the Network Security Groups (NSG). See docs in NSG here
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
I created some GitHub self-hosted runners and would like them to have access to my resources behind a separate virtual network. I know that whitelisting the IP address of the machine will give it access, but I will end up having any number of virtual machines that could be a self-hosted runner, so adding/deleting those IP addresses whitelist for each of my resources seems like a lot of manual work or having automation to whitelist IP addresses to each of my resources when creating the self-hosted runners.
I tried to peer the virtual network that my self-hosted runners would be connected to, to the virtual network of the rest of my resources thinking it would grant access to the self-hosted runners to those resources but I get a 403 firewall error when I attempt any changes or reading of the resource... Am I missing something here? Reading through Microsoft documentation makes it seem like peering the virtual networks would work.
I have bidirectional peering on both Vnets and forward traffic to and from the Vnets in the peering settings. My NSG on both VNet subnets are just the basic one that allows inbound and outbound VNet traffic
https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview
Is there a recommended way of going at this?
If you just want to access the resources in one VNet from another VNet, the network peering is enough. But there is a limitation, there must be no NSG associated with resources or the VNet. If the NSGs exist, you need to add rules to allow the traffics. For example, if the resources are the VMs, then it should work as need. Of course, the firewall inside the VMs should also allow the traffics.
I have the following three virtual networks: - VNETa - VNETb - VNETc All the network traffic between the three virtual networks will be routed through VNET1a.
need to create the virtual networks, and then to ensure that all the Azure virtual machines can connect to other virtual machines by using their private IP address.
The solutions must NOT require any virtual gateways and must minimize the number of peerings. What should you do from the Azure portal before you configuring IP routing?
You could make peering between VNETa and VNETb, peering between VNETa and VNETc. Without a virtual network gateway and without a separate peering connection between those spokes VNETb and VNETc, to make the spoke connectivity, you need to deploy a virtual appliance as the hub in the network VNETa, then make two UDRs in each spoke VNets VNETb and VNETc to route traffic from one spoke network to another spoke network via NVA. In this scenario, you must configure the peering connections to allow forwarded traffic. see the explanation link.
For more details of UDR configuration, you could refer to this blog about Azure Networking - Hub-Spoke with NVA and Azure Firewall
The key to answering this question is to understand that the question is indicating that an IP routing solution will be configured after you have provisioned the necessary resources and configured appropriately: "...before you configure IP routing".
You do not need a gateway subnet or virtual gateways to implement a hub and spoke topology assuming that you are going to provision, for example, a VM with IP Forwarding enabled on the vNIC to act as a router.
Create your 3 subnets, in your example VNETa, VNETb and VNETc
From VNETa, create a peering with VNETb using the Resource Manager Deployment Model
Ensure "Allow forwarded traffic from VNETa to VNETb" is enabled
Repeat steps 2 & 3, substituting VNETb for VNETc
And that's it. Now when you configure IP routing you will provision a router VM or some other Network Virtual Appliance (NVA) in the hub network and create a Route Table for later application to VNETb and VNETc specifying the router VM's internal IP as the next hop.
Jamie.
I have queries related to utilization, distribution and pricing of IP addresses on Azure.
Taking an example, 10.0.0.0/27. It says, 10.0.0.0 - 10.0.0.31 (32 addresses).
After expanding I found as..
CIDR Range: 10.0.0.0/27
Netmask: 255.255.255.224
Wildcard Bits: 0.0.0.31
First IP: 10.0.0.0
Last IP: 10.0.0.31
Total Host: 32
I assigned 10.0.0.0/27 for both VNet and Subnet on Azure Portal.
After creating the virtual network, I see available address 27.
1) No virtual machine created yet, then why the available addresses are 27?
2) What is the IP range for 27 available addresses?
While creating Gateway Subnet, I see errors like...
The specified address space overlaps with subnet 'Subnet1' which has a range of '10.0.0.0/27'.
Your subnet is not contained within the address space for this virtual network: 10.0.0.0/27.
3) How to calculate and decide the available gateway subnet address space for a virtual network?
4) For using gateway subnet, is it mandatory or recommended to add another subnet before or after creating gateway subnet?
5) Why address space is required for creating a gateway subnet? Is gateway subnet not a fixed or static IP address for creating connection?
6) In case of virtual network, 10.0.0.0/27, is pricing done on the basis of utilized IP addresses only?
7) In case of virtual network, 10.0.0.0/27, if there are some un-utilized IP addresses, are they blocked to me or my subscription or un-utilized IP addresses can be used by someone else on his azure portal?
I sincerely request to clarify all seven queries.
Q1-Q3:
Read Azure VNet FAQ, Azure reserves 5 IP addresses within each subnet. These are x.x.x.0-x.x.x.3 and the last address of the subnet. So you have 27 available addresses for the address range 10.0.0.0/27. It's address range 10.0.0.4 - 10.0.0.30
Q4: It's not mandatory for creating Gateway subnet order, you only need to calculate the CIDR Range for each subnet including in your current virtual network address range.
Q5: If you need to configure a virtual network gateway. The gateway subnet contains the IP addresses that the virtual network gateway services use. All gateway subnets must be named GatewaySubnet to work properly. Read here. If you don't need a VPN gateway, you don't need to create Gateway subnet in this VNet.
Q6-Q7: Have a look at Azure VNet pricing and VPN gateway pricing.
Azure Virtual Network is free of charge. Every subscription is allowed
to create up to 50 virtual networks across all regions.
Public IP addresses, and reserved IP addresses used on services inside
a virtual network, are charged.
Network appliances such as VPN Gateway and Application Gateway that
are run inside a virtual network are also charged.
For the un-utilized IP addresses, It looks like unassigned private IP address in your on-premise network. They can continue to be assigned to the resources when you deployed some resources in the VNet or subnet.
For more details, you can read this blog: Understanding CIDR Notation when designing Azure Virtual Networks and Subnets
Azure reserves 5 IP addresses within each subnet. These are x.x.x.0-x.x.x.3 and the last address of the subnet.
x.x.x.0 and the last address of the subnet is reserved for protocol conformance.
x.x.x.1-x.x.x.3 is reserved in each subnet for Azure services.
Address space is the super set of subnets. So, your Address space needs to be bigger and should be able to accommodate the IPs which you are defining for the Subnets.
Basic Subnetting would help.
It is not recommended to deploy your workloads on Gateway subnet. So you need other subnets to deploy your workloads.
Gateways does have a Private IP address which it gets from the Gateway subnet. As I mentioned in Point 2, Address space is the super set of subnets.
Only Public IPs are charged. Private IP which you define in Azure VNET is not charged.
Since it is Private IP address, you can create another 10.0.0.0/27 VNET in the same region. VNET provides a isolation and the address which you define is isolated to that VNET.
I have the following scenario.
2 vnets (same location/location, but different resource groups)
vnetA: Address space 10.1.0.0/16
Gateway subnet 10.1.1.0/24
VM 10.1.0.5
vnetB: Address space 10.0.0.0/16
Gateway subnet 10.0.2.0/24
VM 10.0.1.7
They are both peered through vnet to vnet gateways, but machines cannot ping each other.
Could anyone please guide to documentation or give advice to this please?
You should check the Network Security Groups rules associated to the VNet's Subnets or to the VM's NICs. Unfortunately there is no a specific rule for ICMP protocol, but TCP and UDP only. You have to come up with a rule that suites your needs with the 'any' protocol (i.e. '*').
Instead of using ICMP, when you want to test network connectivity I would suggest to use some TCP protocol based tool like Test-NetConnection and create proper rules in the NSG to let the network traffic pass.