Q:

no stats data on azure application gateway portal overview page when udr is applied

I have a basic setup like this:
VM1(IP:10.0.0.4, VNET1)-------peering------(VNET2)APPGW(standard;frontend:10.10.0.10)--backend(10.10.1.4)

At beginning, there's no UDR on APPGW subnet. On VM1, visit APPGW frontend through cli "curl 10.10.0.10" and can get correct result, also can see stats data like "Sum Total Request" on APPGW portal overview page. 
Then I create a UDR with route item "prefix:0.0.0.0/0 nexthop: 10.0.0.4" and apply this UDR on APPGW subnet. On VM1, still can get correct result with curl command. But on APPGW overview page, can't see stats data for new request.
I remove the UDR on APPGW subnet, and navigate to APPGW overview page, can see the stats data which was related to request in step (2).

My question is:
(1) Why there's no stats data when UDR with default route is apply to APPGW subnet?
(2) As I need to make the default traffic from APPGW to go to 10.0.0.4 first, and also need stats data on portal overview page. What should I do to achieve this?

A:

If you are using Application Gateway V1 SKU, then enable service endpoints for Storage and Event HUB for the application gateway subnet to have diagnostics logs to custom storage account.
For V2 SKU, UDR with default route is not supported. 
Reference: https://docs.microsoft.com/en-us/azure/application-gateway/configuration-overview#user-defined-routes-supported-on-the-application-gateway-subnet 

