EIP and SNAT¶
This configuration is for the network under default VPC, for custom VPC please refer to VPC Gateway
Kube-OVN supports SNAT and EIP functionality at the Pod level using the L3 Gateway feature in OVN. By using SNAT, a group of Pods can share an IP address for external access. With the EIP feature, a Pod can be directly associated with an external IP. External services can access the Pod directly through the EIP, and the Pod will also access external services through this EIP.
Preparation¶
- In order to use the OVN's L3 Gateway capability, a separate NIC must be bridged into the OVS bridge for overlay and underlay network communication. The host must have other NICs for management.
- Since packets passing through NAT will go directly to the Underlay network, it is important to confirm that such packets can pass safely on the current network architecture.
- Currently, there is no conflict detection for EIP and SNAT addresses, and an administrator needs to manually assign them to avoid address conflicts.
Create Config¶
Create ConfigMap ovn-external-gw-config
in kube-system
Namespace:
apiVersion: v1
kind: ConfigMap
metadata:
name: ovn-external-gw-config
namespace: kube-system
data:
enable-external-gw: "true"
external-gw-nodes: "kube-ovn-worker"
external-gw-nic: "eth1"
external-gw-addr: "172.56.0.1/16"
nic-ip: "172.56.0.254/16"
nic-mac: "16:52:f3:13:6a:25"
enable-external-gw
: Whether to enable SNAT and EIP functions.type
:centrailized
ordistributed
, Default iscentralized
Ifdistributed
is used, all nodes of the cluster need to have the same name NIC to perform the gateway function.external-gw-nodes
: Incentralized
mode,The names of the node performing the gateway role, comma separated.external-gw-nic
: The name of the NIC that performs the role of a gateway on the node.external-gw-addr
: The IP and mask of the physical network gateway.nic-ip
,nic-mac
: The IP and Mac assigned to the logical gateway port needs to be an unoccupied IP and Mac for the physical subnet.
Confirm the Configuration Take Effect¶
Check the OVN-NB status to confirm that the ovn-external
logical switch exists and that the correct address and chassis are bound to the ovn-cluster-ovn-external
logical router port.
# kubectl ko nbctl show
switch 3de4cea7-1a71-43f3-8b62-435a57ef16a6 (external)
port localnet.external
type: localnet
addresses: ["unknown"]
port external-ovn-cluster
type: router
router-port: ovn-cluster-external
router e1eb83ad-34be-4ed5-9a02-fcc8b1d357c4 (ovn-cluster)
port ovn-cluster-external
mac: "ac:1f:6b:2d:33:f1"
networks: ["172.56.0.100/16"]
gateway chassis: [a5682814-2e2c-46dd-9c1c-6803ef0dab66]
Check the OVS status to confirm that the corresponding NIC is bridged into the br-external
bridge:
# kubectl ko vsctl ${gateway node name} show
e7d81150-7743-4d6e-9e6f-5c688232e130
Bridge br-external
Port br-external
Interface br-external
type: internal
Port eth1
Interface eth1
Port patch-localnet.external-to-br-int
Interface patch-localnet.external-to-br-int
type: patch
options: {peer=patch-br-int-to-localnet.external}
Config EIP amd SNAT on Pod¶
SNAT and EIP can be configured by adding the ovn.kubernetes.io/snat
or ovn.kubernetes.io/eip
annotation to the Pod, respectively:
apiVersion: v1
kind: Pod
metadata:
name: pod-snat
annotations:
ovn.kubernetes.io/snat: 172.56.0.200
spec:
containers:
- name: pod-snat
image: docker.io/library/nginx:alpine
---
apiVersion: v1
kind: Pod
metadata:
name: pod-eip
annotations:
ovn.kubernetes.io/eip: 172.56.0.233
spec:
containers:
- name: pod-eip
image: docker.io/library/nginx:alpine
The EIP or SNAT rules configured by the Pod can be dynamically adjusted via kubectl or other tools, remember to remove the ovn.kubernetes.io/routed
annotation to trigger the routing change.
kubectl annotate pod pod-gw ovn.kubernetes.io/eip=172.56.0.221 --overwrite
kubectl annotate pod pod-gw ovn.kubernetes.io/routed-
When the EIP or SNAT takes into effect, the ovn.kubernetes.io/routed
annotation will be added back.
Advanced Configuration¶
Some args of kube-ovn-controller
allow for advanced configuration of SNAT and EIP:
--external-gateway-config-ns
: The Namespace of Configmapovn-external-gw-config
, default iskube-system
。--external-gateway-net
: The name of the bridge to which the physical NIC is bridged, default isexternal
.--external-gateway-vlanid
: Physical network Vlan Tag number, default is 0, i.e. no Vlan is used.
微信群 Slack Twitter Support Meeting