Subnet / Express route question

@JoelP Thank you for reaching out. I understand you wish to know if a custom subnet route can override the route table setup via the gateway subnet. The answer is yes, as documented here.

• When outbound traffic is sent from a subnet, Azure selects a route based on the destination IP address, using the longest prefix match algorithm. For example, a route table has two routes: One route specifies the 10.0.0.0/24 address prefix, while the other route specifies the 10.0.0.0/16 address prefix. Azure directs traffic destined for 10.0.0.5 to the next hop type specified in the route with the 10.0.0.0/24 address prefix. This process occurs because 10.0.0.0/24 is a longer prefix than 10.0.0.0/16, even though 10.0.0.5 falls within both address prefixes. As your subnet route will be more specific. That one will be selected.
• If multiple routes contain the same address prefix, Azure selects the route type, based on the following priority (As for Express route BGP is used for custom routes)
  1. User-defined route
  2. BGP route
  Hope this helps! Please let me know if you have any additional questions. Thank you! ​​Please "Accept the answer" if the information helped you. This will help us and others in the community as well.