I can change the IP address of my Teensy 3.2 using the following code.
IPAddress ip(192,168,1,234);
void ipchange(ipaddr newval)
{
IPAddress new_ip(newval.addr0, newval.addr1, newval.addr2, newval.addr3);
sprintf(szText, "Ip was %u.%u.%u.%u, now %u.%u.%u.%u", ip[0], ip[1], ip[2], ip[3]...