Master cannot access nodeport service on k8s 1.27

Hello everyone :grinning:

Kubernetes version: 1.27
Cloud being used: public cloud
Installation method: binary
Host OS: centos 7.9.2
Kube-Proxy Mode : iptables

My enviroment have 3 machine.

I have chosen Flannel as the CNI tool for my cluster. The podSubnet of my cluster and the network CIDR of Flannel are both set as I am using Flannel version 0.22.0 in vxlan mode. Subsequently, I deployed a test pod with NodePort 30800 on node1. When I use the command [curl], I cannot get any response. However, when I try to curl, I do get a response.

In order to resolve the issue, I performed various checks on my machine, including verifying the firewalld, iptables, and Flannel settings. However, I haven’t been able to identify any problems with my cluster.

Next, I used the nmap command to check my ports and I was able to see the 30800 port on both my master and node 2. The output is as follows:
[root@test-node1 bin]# nmap -p 30000-31000

Starting Nmap 6.40 ( ) at 2023-07-26 15:51 CST
Nmap scan report for test-master (
Host is up (0.00035s latency).
Not shown: 93 closed ports
30800/tcp filtered unknown
After inspecting the logs of Flannel, kube-apiserver, and kube-proxy, I found everything to be normal.

I’m quite perplexed by this issue and I would greatly appreciate any assistance you could provide."