Hello @Steph_Azurebeginner ,
You cannot set/change the default gateway. x.x.x.1: is reserved by Azure for the default gateway as mentioned here.
However, if you want to change any of Azure's default routing, you can do so by creating a route table.
Please refer : https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview
But you can only specify the following next hop types when creating a user-defined route:
Virtual network gateway, Virtual network, Internet, Virtual appliance & None
So, adding an on-prem subnet IP to an UDR next hop would not be possible.
As per the below Site recovery article, you should remove any static persistent routes from your on-prem machines before failover:
https://learn.microsoft.com/en-us/azure/site-recovery/concepts-on-premises-to-azure-networking#prepare-on-premises-machines
Request you to follow the below and try to remove the static persistent routes from your on-prem machines before you fail them over to Azure. That will make sure that post failover it gets the Azure default gateway in it's route print configuration and this will ensure that the routing between subnets works fine.
To view the routing table, run route.exe print.
Check the Persistence Routes section. If there's a persistent route, use the route.exe delete command to remove it.
Kindly let us know if the above helps or you need further assistance on this issue.
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