add keep vip in document (#108)

* Update vip.md

* Update vip.en.md

* Update vip.md

Author: mingoooo

docs/advance/vip.en.md

@@ -58,3 +58,9 @@ static-vip01   10.16.0.121           00:00:00:F0:DB:26                         o
 ```
 
 It can be seen that the VIP has been assigned the expected IP address.
+
+## StatefulSet & Kubevirt VM keep VIP
+
+Specify for `StatefulSet` and `VM` resources, these Pods their owned will reuse the VIP when these Pods recreating.
+
+VM keep VIP must be enable the `keep-vm-ip` param in `kube-ovn-controller`. Refer [Kubevirt VM Fixed Address Settings](../guide/setup-options.en.md#kubevirt-vm)

docs/advance/vip.md

@@ -78,3 +78,9 @@ spec:
     - name: static-ip
       image: docker.io/library/nginx:alpine
 ```
+
+## StatefulSet 和 Kubevirt VM 保留 VIP
+
+针对 `StatefulSet` 和 `VM` 的特殊性，在他们的 Pod 销毁再拉起起后会重新使用之前设置的 VIP。
+
+VM 保留 VIP 需要确保 `kube-ovn-controller` 的 `keep-vm-ip` 参数为 `true`。请参考 [Kubevirt VM 固定地址开启设置](../guide/setup-options.md#kubevirt-vm)