One of the trickier parts about building complex hybrid cloud networks is it’s difficult to troubleshoot scenarios where there’s multiple paths.

GCP doesn’t offer a way to view this in Web UI or CLI (gcloud), but it is accessible via the routers.getRouterStatus() method in the API. This essentially queries a specific cloud router for detailed BGP information. The JSON will look like this. Of most interest is the asPaths list.

{
  "kind": "compute#routerStatusResponse",
  "result": {
    "network": "https://www.googleapis.com/compute/v1/projects/xxx/global/networks/yyy",
    "bestRoutes": [
      {
        "kind": "compute#route",
        "creationTimestamp": "2023-06-14T13:17:31.690-07:00",
        "network": "https://www.googleapis.com/compute/v1/projects/xxx/global/networks/yyy",
        "destRange": "10.20.30.0/24",
        "priority": 100,
        "nextHopIp": "169.254.22.73",
        "nextHopVpnTunnel": "https://www.googleapis.com/compute/v1/projects/xxx/regions/us-east4/vpnTunnels/vpn-0",
        "routeType": "BGP",
        "asPaths": [
          {
            "pathSegmentType": "AS_SEQUENCE",
            "asLists": [
              4200000000
            ]
          }
        ]
      },
      {
        "kind": "compute#route",
        "creationTimestamp": "2023-06-14T13:17:31.690-07:00",
        "network": "https://www.googleapis.com/compute/v1/projects/xxx/global/networks/yyy",
        "destRange": "10.20.30.0/24",
        "priority": 100,
        "nextHopIp": "169.254.22.74",
        "nextHopVpnTunnel": "https://www.googleapis.com/compute/v1/projects/xxx/regions/us-east4/vpnTunnels/vpn-1",
        "routeType": "BGP",
        "asPaths": [
          {
            "pathSegmentType": "AS_SEQUENCE",
            "asLists": [
              4200000000
            ]
          }
        ]
      },
    ]
  }
}