Pods in different nodes don't communicate

General Discussions
1

I deployed a cluster on three Virtualbox virtual machines, with centos 7. My pods are not able to communicate among pods on different nodes but communicate between pods in the same node. Everything seems clean and properly working. I have no error message. Only this warning when I join a worker:

[preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.

But all the pods run normally and services are active.

I use flannel network and I shutdown the firewall for testing but the problem persist.

Cluster information:

Kubernetes version: v1.18.2
Cloud being used: put bare-metal
Installation method: manual
Host OS: Centos 7

2

I had similar issue when my Pod CIDR overlapped with my LAN CIDR. Just ensure that your Pod and Service CIDR do not overlap with the host network CIDR.

3

I’m new with kubernetes, what does it mean exactly?

4

I checked, there is no overlapping between CIDRs, Here is the output of ifconfig in a worker:

cni0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 10.244.2.1  netmask 255.255.255.0  broadcast 0.0.0.0
        inet6 fe80::5815:48ff:fe7d:fa81  prefixlen 64  scopeid 0x20<link>
        ether 5a:15:48:7d:fa:81  txqueuelen 1000  (Ethernet)
        RX packets 124  bytes 9372 (9.1 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 91  bytes 9146 (8.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:0c:00:cf:63  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255
        inet6 fe80::e69d:c80f:a3ae:6e16  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:3f:37:e8  txqueuelen 1000  (Ethernet)
        RX packets 1119  bytes 98076 (95.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1187  bytes 94846 (92.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp0s8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.56.105  netmask 255.255.255.0  broadcast 192.168.56.255
        inet6 fe80::955f:73f:b0b4:759c  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:57:bb:34  txqueuelen 1000  (Ethernet)
        RX packets 17782  bytes 8906393 (8.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12975  bytes 1735669 (1.6 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

flannel.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 10.244.2.0  netmask 255.255.255.255  broadcast 0.0.0.0
        inet6 fe80::e842:b2ff:fea3:261f  prefixlen 64  scopeid 0x20<link>
        ether ea:42:b2:a3:26:1f  txqueuelen 0  (Ethernet)
        RX packets 2898  bytes 281736 (275.1 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2898  bytes 281736 (275.1 KiB)
        TX errors 30  dropped 8 overruns 0  carrier 30  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 2533  bytes 187999 (183.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2533  bytes 187999 (183.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vethb881d3bc: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet6 fe80::e4d4:fbff:feca:4141  prefixlen 64  scopeid 0x20<link>
        ether e6:d4:fb:ca:41:41  txqueuelen 0  (Ethernet)
        RX packets 59  bytes 5272 (5.1 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 29  bytes 2232 (2.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0