Forwarding Address Range to a Subnet in a Peered VNet

Question

Forwarding Address Range to a Subnet in a Peered VNet

Omer Yesil 1

hello,
We are using Azure VNet gateway+express route to connect Azure VNETs with our on-prem. We have one VNET for our Dev1 environment which stays under Dev1 Subscription. And now we want to add another VNET under Dev2 Subscription. Please see the attached diagram for more clear picture.

Unfortunately we are very limited with the IP spaces, 10.1.0.0/23, that is currently assigned to Dev1 VNET. The Dev1 VNET has the following subnets:
. Dev1.SNet1 : 10.1.0.0/27
. Dev1.SNet1 : 10.1.0.32/27

And the Dev2 VNet has the following subnets:
. Dev2.SNet1 : 10.2.0.0/27
. Dev2.SNet1 : 10.2.0.32/2

I would like to know what will be the best way (if there is any) in Azure to forward traffic from an ip range to a peered VNET's Subnets (in my case Dev2 Subnets). For example, forward 10.1.0.96/27 (in Dev1 VNET's IP range) to 10.2.0.0/27 (Dev2.SNet1).

Please note that we currently peered Dev1 VNet with Dev2 VNet, however, we are OK to peer Dev2VNet with the VPN's VNET.

thank you

GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-07T09:05:24.597+00:00

Hello @Omer Yesil ,

When you say forward 10.1.0.96/27 (in Dev1 VNET's IP range) to 10.2.0.0/27 (Dev2.SNet1), what exactly you are referring to? I see you have 10.1.0.0/27 & 10.1.0.32/27 subnets in Dev1 Vnet and no other subnets. But Dev1 Vnet is 10.1.0.0/23 which means it has an IP range of 10.1.0.0 - 10.1.1.255 and it includes 10.1.0.96/27 & 10.1.0.128/27. Also Dev1 and Dev2 Vnets are peered with each other which means they can talk to each other.

So my question is what exactly is your requirement? Do you want to make sure that Dev2 Vnet should be able to talk to VPN Vnet or forward the Dev1 Vnet traffic to Dev2 Vnet?

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-07T14:41:23.59+00:00

thank you for the response @GitaraniSharma-MSFT

"Do you want to make sure that Dev2 Vnet should be able to talk to VPN Vnet"

Partially Yes. Our requirement is to enable resources in Dev2 VNet to talk to on-prem and vice versa. As we can only have 10.1.0.0/23 (on-prem gateway dictates this), which is occupied by the Dev1 VNet, we were looking into options to route partial IP ranges of 10.1.0.0/23 to Dev2VNet.

Also, I haven't put the exact architecture (names, subnets..), so answering to your another questions, we have more subnets under the Dev1.VNET. And we have only 3-4 free 10.1.x.y/27 address spaces available (not assigned to a subnet). We want to use these free address spaces for Dev2/Vnet.

hopefully I was able to explain.

cheers
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-11T09:06:48.127+00:00

Hello @Omer Yesil ,

I am still a bit confused about the setup but if your requirement is to enable resources in Dev2 VNet to talk to on-prem and vice versa, then the best approach is to peer Dev2 Vnet with the VPN Vnet with gateway transit feature.

Thanks,
Gita
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-15T11:55:48.837+00:00

Hello @Omer Yesil ,

Following up to check for an update on this post. Could you please provide your inputs on the discussion so far?

Thanks,
Gita
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-20T17:03:18.187+00:00

Hello @Omer Yesil ,

Could you please provide an update on this post?

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-22T03:42:12.89+00:00

Hi Gita,
We have new IP range assigned from on-prem network for the Dev2, therefore our issue has been resolved.

thank you and stay safe
Omer
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-22T09:45:45.627+00:00

Hello @Omer Yesil ,

Thank you for the update. Glad to hear that the issue is resolved.

I believe you were trying to assign the available Dev1 Vnet address spaces to Dev2 Vnet but since they were peered, overlapping address space would have caused issues and hence assigning a new address space is the best way to avoid complications.

We are closing this issue for now.

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-24T02:11:37.8+00:00

yes, that was the case.

Your answer

GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-07T09:05:24.597+00:00

Hello @Omer Yesil ,

When you say forward 10.1.0.96/27 (in Dev1 VNET's IP range) to 10.2.0.0/27 (Dev2.SNet1), what exactly you are referring to? I see you have 10.1.0.0/27 & 10.1.0.32/27 subnets in Dev1 Vnet and no other subnets. But Dev1 Vnet is 10.1.0.0/23 which means it has an IP range of 10.1.0.0 - 10.1.1.255 and it includes 10.1.0.96/27 & 10.1.0.128/27. Also Dev1 and Dev2 Vnets are peered with each other which means they can talk to each other.

So my question is what exactly is your requirement? Do you want to make sure that Dev2 Vnet should be able to talk to VPN Vnet or forward the Dev1 Vnet traffic to Dev2 Vnet?

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-07T14:41:23.59+00:00

thank you for the response @GitaraniSharma-MSFT

"Do you want to make sure that Dev2 Vnet should be able to talk to VPN Vnet"

Partially Yes. Our requirement is to enable resources in Dev2 VNet to talk to on-prem and vice versa. As we can only have 10.1.0.0/23 (on-prem gateway dictates this), which is occupied by the Dev1 VNet, we were looking into options to route partial IP ranges of 10.1.0.0/23 to Dev2VNet.

Also, I haven't put the exact architecture (names, subnets..), so answering to your another questions, we have more subnets under the Dev1.VNET. And we have only 3-4 free 10.1.x.y/27 address spaces available (not assigned to a subnet). We want to use these free address spaces for Dev2/Vnet.

hopefully I was able to explain.

cheers
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-11T09:06:48.127+00:00

Hello @Omer Yesil ,

I am still a bit confused about the setup but if your requirement is to enable resources in Dev2 VNet to talk to on-prem and vice versa, then the best approach is to peer Dev2 Vnet with the VPN Vnet with gateway transit feature.

Thanks,
Gita
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-15T11:55:48.837+00:00

Hello @Omer Yesil ,

Following up to check for an update on this post. Could you please provide your inputs on the discussion so far?

Thanks,
Gita
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-20T17:03:18.187+00:00

Hello @Omer Yesil ,

Could you please provide an update on this post?

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-22T03:42:12.89+00:00

Hi Gita,
We have new IP range assigned from on-prem network for the Dev2, therefore our issue has been resolved.

thank you and stay safe
Omer
GitaraniSharma-MSFT 50,186 Reputation points Microsoft Employee Moderator

2021-01-22T09:45:45.627+00:00

Hello @Omer Yesil ,

Thank you for the update. Glad to hear that the issue is resolved.

I believe you were trying to assign the available Dev1 Vnet address spaces to Dev2 Vnet but since they were peered, overlapping address space would have caused issues and hence assigning a new address space is the best way to avoid complications.

We are closing this issue for now.

Thanks,
Gita
Omer Yesil 1 Reputation point

2021-01-24T02:11:37.8+00:00

yes, that was the case.

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Forwarding Address Range to a Subnet in a Peered VNet

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