I have a MySQL database running on an Ubuntu box that pings 250 clients once a minute (24x7). My column names are:

ip_address varchar(16),
status varchar(7),
timestamp datetime 

Been running it for several weeks and it has grown (10,581,421+ rows). I run a query to return the most recent 800 results on a specific IP address:

SELECT *
FROM (
    SELECT Device_ip, Status, timestamp
    FROM ping_results
    where Device_ip = '192.168.1.1'
    order by timestamp desc
    LIMIT 800
) SUB ORDER BY timestamp asc;

It takes 10+ seconds to return the results. Is there anything I can do differently to speed this up?