Hello All,
I had been trying to figure out how the stuff works in the background for UDR in a specific scenario. Any info on the packet flow will be helpful. Here is the scenario:
1. We have subnet 2 (10.0.2.0/24) and subnet 3 (10.0.3.0/24)
2. UDR applied for both subnet 2 and 3 … 0.0.0.0/0 Next hop ip is 10.0.2.254 (Third Party/Partner Security VM appliance IP)..
3. Now there are two VM in subnet 2 , with IP VM A 10.0.2.34 and VM B 10.0.2.35….
4. VM A sends some packet to VM B… Azure routing service as per UDR will say send traffic to 10.0.2.254 which is Third party appliance. Third Party VM will receive traffic
5. Third Party Appliance at this point will filter and check routing table to send traffic to destination. Routing table will show connected routed 10.0.2.0/24 with gateway IP 10.0.2.1 (which is Azure routing service, for eery subnet created azure reserves first three IP and uses it as subnet gateway IP, most probably using VRRP)..
6. Azure routing service again will see UDR applied and will say that your next hop IP is 10.0.2.254 which is Third Party VM.. So this will become a loop.. won’t it ?
