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CharlesTiu avatar image
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CharlesTiu asked AndreasBaumgarten edited

NIC Effective Routes

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.

azure-virtual-network
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learn2skills avatar image
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learn2skills answered

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://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview


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CharlesTiu avatar image
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CharlesTiu answered AndreasBaumgarten converted comment to answer

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?

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AndreasBaumgarten avatar image
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AndreasBaumgarten answered AndreasBaumgarten edited

anonymous user ,

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

  1. User-defined routes

  2. BGP prpogated routes

  3. System routes

86065-image.png

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


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Regards
Andreas Baumgarten



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