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Copy file name to clipboardExpand all lines: articles/expressroute/designing-for-disaster-recovery-with-expressroute-privatepeering.md
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@@ -109,7 +109,7 @@ When you have a large distributed enterprise network, you're likely to have mult
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Let's consider the example illustrated in the following diagram. In the example, Contoso has two on-premises locations connected to two Contoso IaaS deployment in two different Azure regions via ExpressRoute circuits in two different peering locations.
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:::image type="content" source="./media/designing-for-disaster-recovery-with-expressroute-pvt/multi-region.png" alt-text="Diagram of large distributed on-premises network considerations.":::
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How we architect the disaster recovery has an impact on how cross-regional to cross location (region1/region2 to location2/location1) traffic is routed. Let's consider two different disaster architectures that routes cross region-location traffic differently.
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Scenario 1 is illustrated in the following diagram. In the diagram, green lines indicate paths for traffic flow between VNet1 and on-premises networks. The blue lines indicate paths for traffic flow between VNet2 and on-premises networks. Solid lines indicate desired path in the steady-state and the dashed lines indicate traffic path in the failure of the corresponding ExpressRoute circuit that carries steady-state traffic flow.
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:::image type="content" source="./media/designing-for-disaster-recovery-with-expressroute-pvt/multi-region-arch1.png" alt-text="Diagram of traffic flow for first scenario.":::
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You can architect the scenario using connection weight to influence VNets to prefer connection to local peering location ExpressRoute for on-premises network bound traffic. To complete the solution, you need to ensure symmetrical reverse traffic flow. You can use local preference on the iBGP session between your BGP routers (on which ExpressRoute circuits are terminated on on-premises side) to prefer a ExpressRoute circuit. The solution is illustrated in the following diagram.
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:::image type="content" source="./media/designing-for-disaster-recovery-with-expressroute-pvt/multi-region-sol1.png" alt-text="Diagram of active-active ExpressRoute circuits solution 1.":::
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### Scenario 2
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The Scenario 2 is illustrated in the following diagram. In the diagram, green lines indicate paths for traffic flow between VNet1 and on-premises networks. The blue lines indicate paths for traffic flow between VNet2 and on-premises networks. In the steady-state (solid lines in the diagram), all the traffic between VNets and on-premises locations flow via Microsoft backbone for the most part, and flows through the interconnection between on-premises locations only in the failure state (dotted lines in the diagram) of an ExpressRoute.
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:::image type="content" source="./media/designing-for-disaster-recovery-with-expressroute-pvt/multi-region-arch2.png" alt-text="Diagram of traffic flow for second scenario.":::
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The solution is illustrated in the following diagram. As illustrated, you can architect the scenario either using more specific route (Option 1) or AS-path prepend (Option 2) to influence VNet path selection. To influence on-premises network route selection for Azure bound traffic, you need configure the interconnection between the on-premises location as less preferable. How you configure the interconnection link as preferable depends on the routing protocol used within the on-premises network. You can use local preference with iBGP or metric with IGP (OSPF or IS-IS).
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:::image type="content" source="./media/designing-for-disaster-recovery-with-expressroute-pvt/multi-region-arch2.png" alt-text="Diagram of active-active ExpressRoute circuits solution 2.":::
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> [!IMPORTANT]
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> When one or multiple ExpressRoute circuits are connected to multiple virtual networks, virtual network to virtual network traffic can route via ExpressRoute. However, this is not recommended. To enable virtual network to virtual network connectivity, [configure virtual network peering](../virtual-network/virtual-network-manage-peering.md).
@@ -147,13 +148,6 @@ In this article, we discussed how to design for disaster recovery of an ExpressR
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