Hello, how is it possible that arp and ifconfig return two different macaddress?

Kubernetes-Slack Discussions
#1

Pier. C.:
Hello, how is it possible that arp and ifconfig return two different macaddress?
image.png

#2

Pier. C.:

image.png

#3

Pier. C.:
c4:07 vs c4:09

c4:09 has been onbtained running:

ssh node01
ifconfig
#4

Pier. C.:

image.png

#5

Pier. C.:

image.png

#6

Pier. C.:
the internal ip is 10.17.196.9

#7

Pier. C.:

image.png

#8

Pier. C.:
question 6 in https://kodekloud.com/topic/practice-test-explore-environment-2/

For some reason the internal ip seen by the kubelet is 10.17.196.9 but then running arp/ssh is using this ip for the connection 196.7

Any suggestion to understand better what is happening?

#9

unnivkn:
Hi @Pier. C. fyi:

IP-Mimatch-Question.png
IP-Mimatch-Question.png1756×751 210 KB

IP-Mimatch-Answer-2.png
IP-Mimatch-Answer-2.png1232×115 6.93 KB

IP-Mimatch-Answer-1.png

#10

Pier. C.:
Hello @unnivkn, in your example i see the same behaviour:
ARP provide the macaddress of an ip (248.8) that is different from the INTERNAL-IP seen by the kubelet (248.9). Why?

#11

Pier. C.:
I see that node01 has 2 IP, and two macaddr referring to the same Interface (eth0)
in my example 196.8 and 196.9 refer to node01

#12

Pier. C.:

image.png

#13

Pier. C.:
So the question is. Based on what should I prefer to provide one of the two mac-address?

#14

unnivkn:
it may be an alias, that why in my case both .8 and .9 points to node01, so you can ignore it