curl -L http://etcdurl:2379/v2/keys/flannel/network/config -XPUT -d value="{"Network":"172.16.0.0/16","SubnetLen":24,"Backend":{"Type":"vxlan","VNI":1}}"

[Service]
Type=notify
EnvironmentFile=/etc/sysconfig/flanneld
ExecStart=/usr/bin/flanneld-start $FLANNEL_OPTIONS
ExecStartPost=/opt/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker

DOCKER_OPT_BIP="--bip=10.251.81.1/24"
DOCKER_OPT_IPMASQ="--ip-masq=false"
DOCKER_OPT_MTU="--mtu=1450"
DOCKER_NETWORK_OPTIONS=" --bip=10.251.81.1/24 --ip-masq=false --mtu=1450"

[Service]
Type=notify
NotifyAccess=all
EnvironmentFile=-/run/flannel/docker
EnvironmentFile=-/etc/sysconfig/docker

 #ip route  show dev flannel.1
10.254.50.0/24 via 10.254.50.0 onlink
10.254.60.0/24 via 10.254.60.0 onlink

# ip neig show dev flannel.1
10.254.50.0 lladdr ba:10:0e:7b:74:89 PERMANENT
10.254.60.0 lladdr 92:f3:c8:b2:6e:f0 PERMANENT

# bridge fdb show dev flannel.1
92:f3:c8:b2:6e:f0 dst 10.100.139.246 self permanent
ba:10:0e:7b:74:89 dst 10.100.139.247 self permanent

/proc/sys/net/ipv4/neigh/$NIC/ucast_solicit

/proc/sys/net/ipv4/neigh/$NIC/app_solicit

# cat   /proc/sys/net/ipv4/neigh/flannel.1/app_solicit
3

func newSubnetManager() (subnet.Manager, error) {if opts.kubeSubnetMgr {return kube.NewSubnetManager(opts.kubeApiUrl, opts.kubeConfigFile)}cfg := &etcdv2.EtcdConfig{Endpoints: strings.Split(opts.etcdEndpoints, ","),Keyfile:   opts.etcdKeyfile,Certfile:  opts.etcdCertfile,CAFile:    opts.etcdCAFile,Prefix:    opts.etcdPrefix,Username:  opts.etcdUsername,Password:  opts.etcdPassword,}// Attempt to renew the lease for the subnet specified in the subnetFileprevSubnet := ReadCIDRFromSubnetFile(opts.subnetFile, "FLANNEL_SUBNET")return etcdv2.NewLocalManager(cfg, prevSubnet)}

func init() {backend.Register("vxlan", New)

 func init() {backend.Register("udp", New)}

    # cat /run/flannel/subnet.env
FLANNEL_NETWORK=10.254.0.0/16
FLANNEL_SUBNET=10.254.44.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true

   func (nw *network) handleSubnetEvents(batch []subnet.Event) {. . .switch event.Type {//如果是有新的网段加入（新的主机加入）case subnet.EventAdded:. . .//更新路由表
if err := netlink.RouteReplace(&directRoute); err != nil {log.Errorf("Error adding route to %v via %v: %v", sn, attrs.PublicIP, err)continue}
//添加arp表
log.V(2).Infof("adding subnet: %s PublicIP: %s VtepMAC: %s", sn, attrs.PublicIP, net.HardwareAddr(vxlanAttrs.VtepMAC))if err := nw.dev.AddARP(neighbor{IP: sn.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {log.Error("AddARP failed: ", err)continue}//添加FDB表if err := nw.dev.AddFDB(neighbor{IP: attrs.PublicIP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {log.Error("AddFDB failed: ", err)if err := nw.dev.DelARP(neighbor{IP: event.Lease.Subnet.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {log.Error("DelARP failed: ", err)}continue}//如果是删除实践case subnet.EventRemoved:
//删除路由if err := netlink.RouteDel(&directRoute); err != nil {log.Errorf("Error deleting route to %v via %v: %v", sn, attrs.PublicIP, err)} else {log.V(2).Infof("removing subnet: %s PublicIP: %s VtepMAC: %s", sn, attrs.PublicIP, net.HardwareAddr(vxlanAttrs.VtepMAC))//删除arp            if err := nw.dev.DelARP(neighbor{IP: sn.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {log.Error("DelARP failed: ", err)}//删除FDBif err := nw.dev.DelFDB(neighbor{IP: attrs.PublicIP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {log.Error("DelFDB failed: ", err)}if err := netlink.RouteDel(&vxlanRoute); err != nil {log.Errorf("failed to delete vxlanRoute (%s -> %s): %v", vxlanRoute.Dst, vxlanRoute.Gw, err)}}default:log.Error("internal error: unknown event type: ", int(event.Type))}}}