[Ibonic]

if the proxies aren't truly anonymous, the originator IP is still able to be seen, and may even be logged in some cases (X-Forward is one way)

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even if you could change the IP address, it would have to be one that your ISP owns and allows to be assigned for your connection... so usually if your IP class is banned, "changing" it isn't going to matter unless you switch ISPs or happen to be lucky enough to find a completely different block that your ISP allows be assigned

with my DSL connection, it's not even really possible (without splicing outside phone lines etc.) to set my IP to anything else because their network is set up to only allow this IP to be used from my phone line/number, and the same applies to the other people who use it -- although that doesn't apply to most connections, I guess

also, if your ISP uses DHCP to assign your IP and you try to set the IP manually, it usually doesn't work out well .. especially if someone else is using or ends up using the same IP as the one you choose (sometimes it won't even allow manual settings and the data won't go through to any outside network, even though it seems to be connected)