ok lets clarify something here real fast
if your using a router this will NOT WORK, as you are just renewing your internal IP
furthermore, 9 times out of 10 even if you do this to your modem .."release/renew or reboot" this will not work, that is unless you release it for about 4-12 hours, the reason being that your mac addy is still in the dhcp server that your isp uses and it will just reissue you your same ip again
if you are using DSL it is a little more forgiving depending on your ISP as some like to issue a new one every time your modem goes offline ... others do not
its a crap shoot if it will work for you, and even if it does it honestly isnt really worth it, as you can switch a proxy 10x faster than you can release/renew