Geographic Diversity

Geographic redundancy

To prevent issues arising from unbalanced latency, you should terminate both the primary and secondary connection of an ExpressRoute circuit in the same geographic area.

https://docs.microsoft.com/en-us/azure/expressroute/expressroute-optimize-routing

https://docs.microsoft.com/en-us/azure/expressroute/cross-network-connectivity

https://docs.microsoft.com/en-us/azure/expressroute/designing-for-disaster-recovery-with-expressroute-privatepeering

https://docs.microsoft.com/en-us/azure/architecture/reference-architectures/hybrid-networking/expressroute-vpn-failover

https://docs.microsoft.com/en-us/azure/availability-zones/az-overview

https://docs.microsoft.com/en-us/azure/vpn-gateway/create-zone-redundant-vnet-gateway