[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["很难理解","hardToUnderstand","thumb-down"],["信息或示例代码不正确","incorrectInformationOrSampleCode","thumb-down"],["没有我需要的信息/示例","missingTheInformationSamplesINeed","thumb-down"],["翻译问题","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-08-12。"],[],[],null,["# ASN requirements for site-to-site data transfer\n\nIf you are using Network Connectivity Center for site-to-site data transfer, use the following\nbest practices for managing autonomous system numbers (ASNs).\n\nASN assignment\n--------------\n\nAssign ASNs as described in the following sections.\n\n### High availability pairs\n\nHigh availability (HA) pairs constitute one of the following:\n\n- For Cloud Interconnect connections, you provision two attachments to different Edge Availability Domains (EADs). Each EAD equals one shard.\n- For HA VPN, you have two interfaces on the same VPN gateway, where `interface 0` and `interface 1` constitute the two shards.\n- For Router appliance, you have a pair of redundant interfaces connected to the same router appliances.\n\nIn each of these cases, the peers need to go to the same place and offer\nredundant connectivity for each other.\n\n### Cloud Router ASNs\n\nAll Cloud Routers in hybrid spokes that are associated with a single hub must use the same Cloud Router ASN:\n\n- You must configure a Cloud Router to use ASN 16550 if the\n Cloud Router manages Border Gateway Protocol (BGP) sessions for\n Partner Interconnect VLAN attachments.\n\n- You must configure a Cloud Router to use a private ASN as defined\n in [RFC 6996](https://tools.ietf.org/html/rfc6996) if the\n Cloud Router manages BGP sessions for Dedicated Interconnect\n VLAN attachments, HA VPN tunnels, or Router appliances.\n\n- Both [HA shards](#ha-pairs) in each region going to each\n peer must use the same Cloud Router ASN. Also, both shards must\n always be present. Violating this can still work, but such a configuration\n doesn't qualify for SLA.\n\n- You can mix Partner Interconnect (ASN 16550) and other connection\n types as long as there are correctly configured HA pairs for each, as\n mentioned in the previous bullet point.\n\n- You can use different Cloud Router ASNs in different regions.\n\nConsequently, in addition to the peer ASN requirements:\n\n- You can connect any combination of hybrid spokes for\n Dedicated Interconnect VLAN attachments, HA VPN\n tunnels, or Router appliances to the same hub, as long as the\n Cloud Routers that manage the corresponding BGP sessions are\n configured with the same ASN.\n\n- A hybrid spoke for a Partner Interconnect VLAN attachment can only be\n connected to a hub with other Partner Interconnect VLAN attachment\n hybrid spokes.\n\nFor additional information, see [Create a Cloud Router to connect a\nVPC network to a peer\nnetwork](/network-connectivity/docs/router/how-to/create-router-vpc-on-premises-network).\n\n### Peer ASNs\n\nAll non-Google peering routers that are associated with a single spoke must use the same ASN when advertising prefixes to the Cloud Router. This is important because, if two peers advertise the same prefix with different ASNs or AS paths, only one peer's ASN and AS path is readvertised for that prefix. Different spokes must have different ASNs. That is, if two BGP sessions belong to different spokes, they must have different ASNs.\n\n### Example\n\nSuppose that your Network Connectivity Center setup uses the following spokes:\n\n- Spoke `A-east` includes VPN tunnels `1` and `2`. It uses Cloud Router `A`.\n- Spoke `B-west` includes VPN tunnels `3` and `4`. It uses Cloud Router `B`.\n\nBecause all spokes connect to the same hub, Cloud Router `A` and\nCloud Router `B` must both use the same\nnumber---for example, `65000`---in the `bpg.asn` field.\n\nIn this same scenario, your setup includes the following on-premises routers:\n\n- Peer router `A1-east` is associated with spoke `A-east` and Cloud Router `A`.\n- Peer router `A2-east` is also associated with spoke `A-east` and Cloud Router `A`.\n- Peer router `B1-west` is associated with spoke `B-west` and Cloud Router `B`.\n- Peer router `B2-west` is also associated with spoke `B-west` and Cloud Router `B`.\n\nBecause peer router `A1-east` and peer router `A2-east` are associated with one\nspoke (spoke `A-east`), they must use the same ASN---for example, `65001`.\nCloud Router `A` also uses this number, in the `bgpPeers.peerAsn` field for\nVPN tunnel `1` and the `bgpPeers.peerAsn` field for VPN tunnel `2`.\n\nSimilarly, peer router `B1-west` and peer router `B2-west` are both associated\nwith one spoke (spoke `B-west`), so they must use the same\nASN---for example, `65002`. Cloud Router `B` also uses this number, in\nthe `bgpPeers.peerAsn` field for VPN tunnel `3` and in the `bgpPeers.peerAsn`\nfield for VPN tunnel `4`.\n\nAS path loop detection\n----------------------\n\nWe recommend configuring autonomous system (AS) path loop detection on your peer\nrouters. This feature is almost always on by default, but if it is not, we\nrecommend that you configure it. When AS path loop detection is enabled, if two\nspokes are configured with the same peer ASN, AS path loop detection on a peer\nrouter for one spoke drops all prefix advertisements from the other spoke.\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 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 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)."]]
