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Network Connectivity Center provides full mesh connectivity between each spoke that has
the data transfer feature enabled. If all spokes have the feature enabled,
Network Connectivity Center propagates all routes that one spoke learns to all other
spokes.
Network Connectivity Center topology (click to enlarge)
In the preceding topology, Spokes A, B, and C are attached to the same hub
and use Cloud Router to advertise prefixes into the hub.
To enable cross-region site-to-site traffic through hubs and spokes, you must
enable global routing
in the VPC network associated with the hub and spokes.
If all spokes are located in the same region, then global routing isn't
necessary because site-to-site traffic works without enabling global routing.
The following table shows how the hub propagates prefix advertisements to
other spokes.
[[["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 2025-08-29 UTC."],[],[],null,["# Route exchange with site-to-site data transfer\n\nNetwork Connectivity Center provides full mesh connectivity between each spoke that has\nthe data transfer feature enabled. If all spokes have the feature enabled,\nNetwork Connectivity Center propagates all routes that one spoke learns to all other\nspokes.\n[](/static/network-connectivity/docs/network-connectivity-center/images/ncc-topology.svg) Network Connectivity Center topology (click to enlarge)\n\nIn the preceding topology, Spokes A, B, and C are attached to the same hub\nand use Cloud Router to advertise prefixes into the hub.\n\nTo enable *cross-region* site-to-site traffic through hubs and spokes, you must\n[enable global routing](/network-connectivity/docs/router/how-to/create-network-set-modes)\nin the VPC network associated with the hub and spokes.\nIf all spokes are located in the same region, then global routing isn't\nnecessary because site-to-site traffic works without enabling global routing.\n\nThe following table shows how the hub propagates prefix advertisements to\nother spokes.\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 about high availability requirements, see [High availability requirements for spoke resources](/network-connectivity/docs/network-connectivity-center/concepts/high-availability).\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 [Work 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)."]]
