Hello @Fluchtmann, Gunnar !
Welcome to Microsoft QnA!
I understand that you need to connect Cisco Gateway with Azure via VPN
Azure supports VPN with Cisco
Sample links for Help
https://learn.microsoft.com/en-us/azure/vpn-gateway/tutorial-site-to-site-portal
https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-3rdparty-device-config-cisco-asa
On Azure you must create a Local Network Gateway which represents Cisco Device
Then you can configure the local network gateway settings to match the remote information provided by the Cisco gateway. This can be done in the "Local network gateway" section of the Virtual network gateway configuration in Azure.
When you create the Local Gateway ( Again it represents the On Premises Device) , you can set address space and tye of routing (Policy or route based)
You may need to configure the "Connection type" setting to be "Policy-based" instead of "Route-based" in order to match the Cisco gateway configuration.
I hope this helps!
Kindly mark the answer as Accepted and Upvote in case it helped!
Regards