Connected phone to mac using usb0, but IP address attached to the device is linked to the mac

I have a Nokia N900 that's running Maemo (based on Debian Lenny).

I am connecting it to my Mac using USB. On the Nokia I run ifup usb0. In /etc/network/interfaces I have:

iface usb0 inet static
address 192.168.2.18
netmask 255.255.255.0
gateway 192.168.2.17

I connect it to my computer using USB and I get the following:

But, when I run nmap on the IP address 192.168.2.17 from my mac with the -sV option it's displaying: 22/tcp open ssh OpenSSH 6.9 (protocol 2.0)

… This isn't the version of OpenSSH that's running on the phone. The version on the phone is 5.1. This is the same version that's running on my mac.

Some how that IP is linked to my mac.

If I use the IP address 192.168.2.18 I get a warning saying the IP address is already used on the network. I've tried changing the IP on the phone in the interfaces file, but it does the same thing each time.

Any ideas what's going on?

netstat -nr from the mac (excluding ipv6):

Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
default            192.168.1.1        UGSc          632        7     en1
127                127.0.0.1          UCS             1        0     lo0
127.0.0.1          127.0.0.1          UH              3     5737     lo0
169.254            link#6             UCS             1        0     en1
192.168.1          link#6             UCS             1        0     en1
192.168.1.1/32     link#6             UCS            12        0     en1
192.168.1.1        74:a5:28:f0:f8:9d  UHLWIir       125      258     en1   1186
192.168.1.5/32     link#6             UCS             2        0     en1
192.168.1.5        28:f0:76:4:db:80   UHLWIi          1       16     lo0
224.0.0            link#6             UmCS            2        0     en1
224.0.0.251        1:0:5e:0:0:fb      UHmLWI          1        0     en1
255.255.255.255/32 link#6             UCS             1        0     en1