High availability requirements for spoke resources
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For Network Connectivity Center to properly enable site-to-site data transfer, you must
configure spoke resources in high availability configurations. If you don't,
sites might be unable to pass traffic to one another.
Each resource type has different requirements for high availability, as
described in the following sections.
High availability for Cloud Interconnect
For site-to-site data transfer to work correctly with
Cloud Interconnect resources, you must configure multiple Interconnect
connections, each in a separate edge availability domain.
For detailed information about how to configure Cloud Interconnect
resources for high availability, see the following documentation:
For site-to-site data transfer to work correctly with Cloud VPN
resources, you must configure multiple HA VPN gateway interfaces
and tunnels to achieve a 99.99% SLO. For guidance, see the
Cloud VPN overview.
High availability for Router appliance
For site-to-site data transfer to work correctly with router appliance instances
attached to a spoke, you must do the following:
If you place all your router appliance instances in a single spoke,
use equal-cost multipath (ECMP) to advertise the same set of prefixes from
two router appliance instances. To advertise different prefixes for each
spoke, add each router appliance instance to a different spoke.
You can't create a cross-region configuration in a single spoke.
ECMP is the result of advertising the same prefix or prefixes, with
the same MEDs and AS path as applicable, from two or more
router appliance instances. The guidance about
route selection in VPC networks
applies to router appliance instances as it does to other
Google Cloud resources.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-28 UTC."],[],[],null,["# High availability requirements for spoke resources\n\nFor Network Connectivity Center to properly enable site-to-site data transfer, you must\nconfigure spoke resources in high availability configurations. If you don't,\nsites might be unable to pass traffic to one another.\n\nEach resource type has different requirements for high availability, as\ndescribed in the following sections.\n\nHigh availability for Cloud Interconnect\n----------------------------------------\n\nFor site-to-site data transfer to work correctly with\nCloud Interconnect resources, you must configure multiple Interconnect\nconnections, each in a separate edge availability domain.\n\nFor detailed information about how to configure Cloud Interconnect\nresources for high availability, see the following documentation:\n\n- [Redundancy and SLA for\n Dedicated Interconnect](/network-connectivity/docs/interconnect/concepts/dedicated-overview#redundancy)\n- [Establishing 99.99% availability for\n Dedicated Interconnect](/network-connectivity/docs/interconnect/tutorials/dedicated-creating-9999-availability)\n- [Redundancy and SLA for\n Partner Interconnect](/network-connectivity/docs/interconnect/concepts/partner-overview#redundancy)\n- [Establishing 99.99% availability for\n Partner Interconnect](/network-connectivity/docs/interconnect/tutorials/partner-creating-9999-availability)\n- [Creating redundant Interconnect connections with sufficient\n capacity](/network-connectivity/docs/interconnect/concepts/best-practices#capacity)\n\nHigh availability for Cloud VPN\n-------------------------------\n\nFor site-to-site data transfer to work correctly with Cloud VPN\nresources, you must configure multiple HA VPN gateway interfaces\nand tunnels to achieve a 99.99% SLO. For guidance, see the\n[Cloud VPN overview](/network-connectivity/docs/vpn/concepts/overview#ha-vpn).\n\nHigh availability for Router appliance\n--------------------------------------\n\nFor site-to-site data transfer to work correctly with router appliance instances\nattached to a spoke, you must do the following:\n\nIf you place all your router appliance instances in a single spoke,\nuse equal-cost multipath (ECMP) to advertise the same set of prefixes from\ntwo router appliance instances. To advertise different prefixes for each\nspoke, add each router appliance instance to a different spoke.\n\nYou can't create a cross-region configuration in a single spoke.\n\nECMP is the result of advertising the same prefix or prefixes, with\nthe same MEDs and AS path as applicable, from two or more\nrouter appliance instances. The guidance about\n[route selection in VPC networks](/vpc/docs/routes#routeselection)\napplies to router appliance instances as it does to other\nGoogle Cloud resources.\n\nFor detailed information about how to configure router appliance instances\nfor high availability, see\n[requirements for 99.9% availability](/network-connectivity/docs/network-connectivity-center/concepts/ra-overview#ra-availability).\n\nWhat's next\n-----------\n\n- To view a sample topology, see [Sample topology for site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/data-transfer-topology).\n- To learn more about how Network Connectivity Center enables full mesh connectivity, see [Route exchange with site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/route-exchange).\n- To work through a tutorial, see [Connecting two sites by using Cloud VPN spokes](/network-connectivity/docs/network-connectivity-center/tutorials/connecting-two-offices-with-vpns).\n- To create hubs and spokes, see [Working with hubs and spokes](/network-connectivity/docs/network-connectivity-center/how-to/working-with-hubs-spokes).\n- To view a list of partners whose solutions are integrated with Network Connectivity Center, see [Network Connectivity Center partners](/network-connectivity/docs/network-connectivity-center/partners)."]]
