I was getting strange IP Adress from my (2nd) router ad figure it out it was I change the ethernet port. Why I was getting strange IP?

I have two Routers, the 2nd a tp-link with dd-wrt. I configure it with the same SSID and other options to have one big wifi network. It worked well. But from one moment to another I was not getting internet.

At first I though I was being hacked. Then I found https://superuser.com/a/1145468/273358 And it turn out my ethernet cable was connected on a different port. Switched it, solve it.

EDIT: the strange IPs were: It was usually 192.168.100.1 for the 2nd router and 192.168.100.4 for my laptop.

But then I got

inet 169.254.83.125 netmask 0xffff0000 broadcast 169.254.255.255 

And I made a ping:

ping 224.0.0.251
PING 224.0.0.251 (224.0.0.251): 56 data bytes
64 bytes from 169.254.83.125: icmp_seq=0 ttl=255 time=0.108 ms
64 bytes from 169.254.193.60: icmp_seq=0 ttl=255 time=92.558 ms

And arp:

$ arp -a
? (169.254.83.125) at x:x:xx:xx:xx:e9 on en7 permanent [ethernet]
? (169.254.193.60) at x:xx:xx:xx:6f on en7 [ethernet]
? (224.0.0.251) at x:xx:xx:xx:xx:fb on en7 ifscope permanent [ethernet]

But I want to know what happened.

What happened was that you were plugged into the wrong port and there was no DHCP server available on the network, and so your device used a self-assigned link-local IP address as defined in RFC3927.