Does Server 2022 Support BGP 4-byte (32-bit) ASNs

Question

We are going through the motion to configure BGP routing on a Windows Server so we can peer with our cisco routers, allowing us to advertise a single address on a loopback for DNS services. Creating an Anycast solution for high availability since some custom applications will not failover gracefully, also simplifying DNS configuration at our locations. We use iBGP internally and therefore use our publicly assigned ASN for internal traffic and would need to peer with the windows server using 4-byte (32-bit) ASNs. I have tried both the built in Powershell as well as installing the 7.3.4 version and in both I get the following error when trying to configure the BGP Router on the windows server (IPs and ASNs have been changed for privacy):

PS C:>Add-BgpRouter -BgpIdentifier "192.168.1.1" -LocalASN 333333

Add-BgpRouter: Cannot validate argument on parameter 'LocalASN'. The 333333 argument is greater than the maximum allowed range of 65534. Supply an argument that is less than or equal to 65534 and then try the command again.

Everything I am reading from the microsoft website does not reference any limitations in the BGP configuration in server 2022, and even notes in Azure they support 4 byte ASN. I have found the configuration file that references the limitation:

C:\Windows\System32\WindowsPowerShell\v1.0\Modules\RemoteAccess\PS_BgpPeer_v1.0

            <Parameter ParameterName="PeerASN">
              <Type PSType="System.UInt32" />
              <CmdletParameterMetadata ValueFromPipelineByPropertyName="true">
                <ValidateNotNull />
                <ValidateNotNullOrEmpty />
                <ValidateRange Min="1" Max="65534" />
              </CmdletParameterMetadata>

Is there another version out there that I might be able to use? Would changing the Max value work? Anyone have a solution?

Answer 1

Hello there,

32-bit ASNs are not officially supported by Microsoft. This issue on git https://github.com/MicrosoftDocs/windows-powershell-docs/issues/962has a user say 32-bit ASNs are not supported, then links to a commit which changes the documentation from not mentioning 32-bit ASNs to saying it does support 32-bit ASNs

Similar discussion here

https://learn.microsoft.com/en-us/answers/questions/92865/32-bit-asns

Hope this resolves your Query !!

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