Default route advertisement from Azure to On Prem via express route

Hi naresh, Yes it's possible to advertise a default route via express Azure ER but the complexity It will depends on your network infrastructure and also in your Express Route provider, based on the information share this is your configuration:

Branch1 (MPLS) ---\
                   \
Branch2 (MPLS) ---- >Azure ER<---> Azure (Forti-FW) <---> Internet
                   /
Branch3 (MPLS) ---/

You could follow below proces:

• Check managed routing: Some connectivity providers offer setting up and managing routing as a managed service. Check with your connectivity provider to see if they offer this service. (On this will depend if you can advertise the default route)
• Chek IP Addressessing: Reserve IP addresses for routing if its required to avoid routing loops.
• Advertise default routes on Azure private peering sessions.
• Implement azure route server

This is the expected configuration: Branch1, 2, 3 (MPLS): These are your on-premises networks located at different sites. They are all connected to Azure via MPLS. Azure ExpressRoute (BGP Propagation, Advertise Default Route): Set up BGP parameters on your your ExpressRoute circuit and advertise the 0.0.0.0/0. If you don't have the option to advertise the default route by BGP , you will need to manually configure static routes on each router in your network(Becarefull) Azure Route Server-Optional(RS): Can simplify the management of routing information between your network virtual appliance (NVA) and your virtual network Azure Fortinet Firewall(Forti-FW): They’re responsible for routing traffic between your on-premises network and the internet. Internet: This is the destination for your internet-bound traffic.

Branch1(MPLS)---\
                 \
Branch2(MPLS)----- > Az ER(BGP Propagation, Advertise DR) <--->Az(Forti-FW,RS)<---> Internet
                 /
Branch3(MPLS)---/

This is MS documentation to achieve that:

• https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-howto-circuit-portal-resource-manager
• https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-routing
• https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-faqs#how-are-vnets-advertised-on-expressroute-private-peering
• https://video2.skills-academy.com/en-us/azure/virtual-network/virtual-networks-udr-overview
• https://video2.skills-academy.com/en-us/azure/route-server/route-server-faq

I hope this information help you. Regards, Luis

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