I live on campus and use a university secured 802.1x wifi network. The first question I have is, what's the difference between the IP address I can see from ifconfig and the address that is show as username@[email protected]? Since they both change does DHCP assign me both of them? Also is there a way to find this second, ssh usable address from the terminal? I can't seem to find a way to figure out how to make this ssh address static, so at least I'd like create a cronjob that copies and pastes it to a txt file on my cloud drive.

Image of the address I'm talking about just for clarification:

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If anyone knows how to make this static without router access on a 802.1x network that'd be super helpful also.

1 Answer 1


It's the PTR record (reverse DNS) corresponding to the IP address which your computer was assigned via DHCP. It changes each time your computer gets a new address from DHCP and you can't make it static.

The problem here is not in the settings on your computer, but on all the other computers connected to the campus network (i.e. computers try to connect to your computer). These machines ask the DNS server (which they also know from the campus DHCP) for the IP address of [email protected] and the DNS server returns the corresponding IP address.

You'd need to make a DHCP reservation to get the same IP address always, but this only administrators can do.

You can check it with command-line:

dig +short -x <your_ip_address>

or if you know your interface name (en0 in the below example) automatically:

dig +short -x `ipconfig getifaddr en0`

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