'Set our IP address'

def setIP(self, ipstr, prefixLen=None):

    if ('/' in ipstr):
        (self.ip, self.prefixLen) = ipstr.split('/')
        return self.ifconfig(ipstr, 'up')
    else:
        if (prefixLen is None):
            raise Exception(('No    prefix    length    set    for    IP    address    %s' % (ipstr,)))
        (self.ip, self.prefixLen) = (ipstr, prefixLen)
        return self.ifconfig(('%s/%s' % (ipstr, prefixLen)))
