Need some fundamental understanding on how the IP addresses are populated on Linux devices

Applications IP Networking
1

I am quite new(5-6 months) to embedded Linux programming in C and python. I have with me 2 Linux based devices connected to a network.
I am trying to collect the IP address generated by the ethernet and wlan interface and populate it on a web application.
Now Device 1 is giving me 2 IP addresses on the wlan interface. This is after I run ip a .

Namely 10.17.36.31/24 and 10.17.36.33/24

And Device 2 is also giving me 2 IP addresses but both are same.

They are both 10.61.44.27/24 and 10.61.44.27/22

Now I can implement the logic to get the correct IP from these 2 results, but I am not able to figure out where these IP addresses are coming from?
I don't have fundamental knowledge on networking, so not able to understand the output of the ip a command.
Any guidance to a material that clearly describes networking in linux devices would be helpful. Specifically on how to understand what the output of ip a signifies. And also what exactly is the difference between scope global and scope global secondary , and what are they? What is brd, what does /24 and /22 mean. Trying to find answers to all these questions.

Device 1:

5: eth0: <NO-CARRIER,BROADCAST,MULTICAST,DYNAMIC,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff
6: wlan0: <BROADCAST,MULTICAST,DYNAMIC,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether bb:cc:aa:ee:dd:gg brd ff:ff:ff:ff:ff:ff
    inet 10.17.36.31/24 brd 10.61.44.255 scope global wlan0
       valid_lft forever preferred_lft forever
    inet 10.17.36.33/24 brd 10.61.47.255 scope global secondary wlan0
       valid_lft forever preferred_lft forever
    inet6 aaaa::bbbb:2222:ffff:eeee/64 scope link
       valid_lft forever preferred_lft forever

Device 2:

5: eth0: <NO-CARRIER,BROADCAST,MULTICAST,DYNAMIC,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff
6: wlan0: <BROADCAST,MULTICAST,DYNAMIC,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether bb:cc:aa:ee:dd:gg brd ff:ff:ff:ff:ff:ff
    inet 10.61.44.27/24 brd 10.61.44.255 scope global wlan0
       valid_lft forever preferred_lft forever
    inet 10.61.44.27/22 brd 10.61.47.255 scope global wlan0
       valid_lft forever preferred_lft forever
    inet6 aaaa::bbbb:2222:ffff:eeee/64 scope link
       valid_lft forever preferred_lft forever
2

Can you show output of ip route show as these settings look confusing, especially for device 2.
Have you had a subnet expansion in your network from /24 to /22 perhaps ?

What linux distribution is on those devices ?

Regards
Peasant.

3

It is a standard yocto based distribution.
Let me check on the subnet expansion and come back to that.

This is the output of ip route show from Device 2

default via 10.61.44.1 dev wlan0
10.61.44.0/24 dev wlan0 proto kernel scope link src 10.61.44.27
10.61.44.0/22 dev wlan0 proto kernel scope link src 10.61.44.27
4

Does this give any clue?

5

Can that make sense, two times the same IP addr? And with different subnet masks?

7

Is this a domestic or business configuration?

Is there more than one connection to the internet?

Do you know where this 10.61.44.0 ip address is coming from? Do you have a local DHCP server? Or is this ip address coming from the web somehow? Or have you set this as a static ip address yourself? Or have you not configured any network parameters since installing yocto and this is default?

8

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