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Balkrishna Pandey
Balkrishna Pandey

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How to show ethernet interfaces of the pod and ping other pods?

#kubernetes #cka

There are multiple ways to get the IP address of a particular pod. One way is using kubectl describe command as follows:


kubectl describe po nginx-776567f984-nkp9z | grep -i ip
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Output:


IP:      172.17.0.14

IPs:

 IP:      172.17.0.14

  Type:          Projected (a volume that contains injected data from multiple sources)
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Another way to get the IP address is using kubectl get command as follows:


kubectl get pods nginx-776567f984-nkp9z -o wide
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Output:


NAME           READY  STATUS  RESTARTS  AGE   IP      NODE    NOMINATED NODE  READINESS GATES

nginx-776567f984-nkp9z  1/1   Running  0     5m16s  172.17.0.14  minikube  <none>      <none>
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Now, let's see how to ping one pod from another. We will first get the name of all the pods that are running with nginx image. For that, we will use the following command:


kubectl get pods -l app=frontend -o wide
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Output:


NAME           READY  STATUS  RESTARTS  AGE  IP      NODE    NOMINATED NODE  READINESS GATES

nginx-776567f984-nkp9z  1/1   Running  0     11m  172.17.0.14  minikube  <none>      <none>

nginx-776567f984-w9bsl  1/1   Running  0     11m  172.17.0.12  minikube  <none>      <none>
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Once we get all the pods, we will copy any one of the pod names and run the exec command as follows:


kubectl exec -ti nginx-776567f984-nkp9z -- bash
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Output:


root@nginx-776567f984-nkp9z:/#
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Now, you are inside the pod. Let's see all the available interfaces using the ifconfig command. I am seeing following error, so ifconfig is not available by default in nginx container.


bash: ifconfig: command not found
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Let's install necessary packages to run ping test,

  • To install the ifconfig, run: apt update and apt install net-tools.

  • To install ping, in the terminal and type: apt install iputils-ping.

Show ethernet interfaces:


ifconfig
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Output:


eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500

    inet 172.17.0.14 netmask 255.255.0.0 broadcast 172.17.255.255

    ether 02:42:ac:11:00:0e txqueuelen 0 (Ethernet)

    RX packets 6315 bytes 9259871 (8.8 MiB)

    RX errors 0 dropped 0 overruns 0 frame 0

    TX packets 1750 bytes 97053 (94.7 KiB)

    TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0



lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536

    inet 127.0.0.1 netmask 255.0.0.0

    loop txqueuelen 1000 (Local Loopback)

    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
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Now, to ping one pod from another, you can use the following command. Notice from the above output we are using the IP of another pod for the ping command.


ping 172.17.0.12
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Output:


PING 172.17.0.12 (172.17.0.12) 56(84) bytes of data.

64 bytes from 172.17.0.12: icmp_seq=1 ttl=64 time=0.055 ms

64 bytes from 172.17.0.12: icmp_seq=2 ttl=64 time=0.118 ms

64 bytes from 172.17.0.12: icmp_seq=3 ttl=64 time=0.117 ms
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