排錯背景：在一次生產環境的部署過程中，配置文件中配置的訪問地址為集群的Service，配置好后發現服務不能正常訪問，遂啟動了一個busybox進行測試，測試發現在busybox中，能通過coredns正常的解析到IP，然后去ping了一下service，發現不能ping通，ping clusterIP也不能ping通。
排錯經歷：首先排查了kube-proxy是否正常，發現啟動都是正常的，然后也重啟了，還是一樣ping不通，然后又排查了網絡插件，也重啟過flannel，依然沒有任何效果。后來想到自己的另一套k8s環境，是能正常ping通service的，就對比這兩套環境檢查配置，發現所有配置中只有kube-proxy的配置有一點差別，能ping通的環境kube-proxy使用了--proxy-mode=ipvs ,不能ping通的環境使用了默認模式（iptables）。
iptables沒有具體設備響應。
然后就是開始經過多次測試，添加--proxy-mode=ipvs 后，清空node上防火牆規則，重啟kube-proxy后就能正常的ping通了。
kubeadm 部署方式修改kube-proxy為 ipvs模式。
默認情況下，我們部署的kube-proxy通過查看日志，能看到如下信息：Flag proxy-mode="" unknown，assuming iptables proxy
# kubectl logs -n kube-system kube-proxy-xxxx W1013 06:55:35.773739 1 proxier.go:513] Failed to load kernel module ip_vs with modprobe. You can ignore this message when kube-proxy is running inside container without mounting /lib/modules W1013 06:55:35.868822 1 proxier.go:513] Failed to load kernel module ip_vs_rr with modprobe. You can ignore this message when kube-proxy is running inside container without mounting /lib/modules W1013 06:55:35.869786 1 proxier.go:513] Failed to load kernel module ip_vs_wrr with modprobe. You can ignore this message when kube-proxy is running inside container without mounting /lib/modules W1013 06:55:35.870800 1 proxier.go:513] Failed to load kernel module ip_vs_sh with modprobe. You can ignore this message when kube-proxy is running inside container without mounting /lib/modules W1013 06:55:35.876832 1 server_others.go:249] Flag proxy-mode="" unknown, assuming iptables proxy I1013 06:55:35.890892 1 server_others.go:143] Using iptables Proxier. I1013 06:55:35.892136 1 server.go:534] Version: v1.15.0 I1013 06:55:35.909025 1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_max' to 131072 I1013 06:55:35.909053 1 conntrack.go:52] Setting nf_conntrack_max to 131072 I1013 06:55:35.919298 1 conntrack.go:83] Setting conntrack hashsize to 32768 I1013 06:55:35.945969 1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_tcp_timeout_established' to 86400 I1013 06:55:35.946044 1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_tcp_timeout_close_wait' to 3600 I1013 06:55:35.946623 1 config.go:96] Starting endpoints config controller I1013 06:55:35.946660 1 controller_utils.go:1029] Waiting for caches to sync for endpoints config controller I1013 06:55:35.946695 1 config.go:187] Starting service config controller I1013 06:55:35.946713 1 controller_utils.go:1029] Waiting for caches to sync for service config controller I1013 06:55:36.047121 1 controller_utils.go:1036] Caches are synced for endpoints config controller I1013 06:55:36.047195 1 controller_utils.go:1036] Caches are synced for service config controller
修改kube-proxy的配置文件,添加mode 為ipvs。默認是空的
# kubectl edit cm kube-proxy -n kube-system ... ipvs: excludeCIDRs: null minSyncPeriod: 0s scheduler: "" strictARP: false syncPeriod: 30s kind: KubeProxyConfiguration metricsBindAddress: 127.0.0.1:10249 mode: "ipvs" ...ipvs模式需要注意的是要添加ip_vs相關模塊，
cat > /etc/sysconfig/modules/ipvs.modules <<EOF #!/bin/bash modprobe -- ip_vs modprobe -- ip_vs_rr modprobe -- ip_vs_wrr modprobe -- ip_vs_sh modprobe -- nf_conntrack_ipv4 EOF
chmod 755 /etc/sysconfig/modules/ipvs.modules && bash /etc/sysconfig/modules/ipvs.modules && lsmod | grep -e ip_vs -e nf_conntrack_ipv4重啟kube-proxy 的pod# kubectl get pod -n kube-system | grep kube-proxy |awk '{system("kubectl delete pod "$1" -n kube-system")}' pod "kube-proxy-62gvr" deleted pod "kube-proxy-n2rml" deleted pod "kube-proxy-ppdb6" deleted pod "kube-proxy-rr9cg" deleted在pod重啟后再查看日志，發現模式已經變為ipvs了。
# kubectl get pod -n kube-system |grep kube-proxy kube-proxy-cbm8p 1/1 Running 0 85s kube-proxy-d97pn 1/1 Running 0 83s kube-proxy-gmq6s 1/1 Running 0 76s kube-proxy-x6tcg 1/1 Running 0 81s # kubectl logs -n kube-system kube-proxy-cbm8p I1013 07:34:38.685794 1 server_others.go:170] Using ipvs Proxier. W1013 07:34:38.686066 1 proxier.go:401] IPVS scheduler not specified, use rr by default I1013 07:34:38.687224 1 server.go:534] Version: v1.15.0 I1013 07:34:38.692777 1 conntrack.go:52] Setting nf_conntrack_max to 131072 I1013 07:34:38.693378 1 config.go:187] Starting service config controller I1013 07:34:38.693391 1 controller_utils.go:1029] Waiting for caches to sync for service config controller I1013 07:34:38.693406 1 config.go:96] Starting endpoints config controller I1013 07:34:38.693411 1 controller_utils.go:1029] Waiting for caches to sync for endpoints config controller I1013 07:34:38.793684 1 controller_utils.go:1036] Caches are synced for endpoints config controller I1013 07:34:38.793688 1 controller_utils.go:1036] Caches are synced for service config controller再次測試ping service就ok了