NIC Effective Routes

Question

Hi, from Network Interfaces, under Support + troubleshooting. there's a effective routes feature.
May I know how did it derives the routes? There isn't any routing tables being define in my environment. We have VPN and expressroute.

I ask because there's a few destination which is under 10.x.x.x which wasn't being define in places I'm aware of.

Answer 1

Hi anonymous user

The effective routes for the network interfaces attached to a virtual machine are a combination of default routes, any routes you've created, and any routes propagated from on-premises networks via BGP through an Azure virtual network gateway.

Azure automatically creates system routes and assigns the routes to each subnet in a virtual network. You can't create system routes, nor can you remove system routes, but you can override some system routes with custom routes. Azure creates default system routes for each subnet, and adds additional optional default routes.

refer- https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview

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Answer 2

anonymous user ,

yes. This is the order how Azure selects the route:

1. User-defined routes
2. BGP prpogated routes
3. System routes

Source: :https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview#how-azure-selects-a-route

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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

Answer 3

I see. Correct me if I'm wrong.

If I didn't create any manual routing. All the routes I saw, is all system routes which I can't make any modification. However I can use custom route to override them?