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The problem is that we have a public OpenVPN service. Pay €9.95 and you get an OpenVPN account at currently half a dozen of servers for a month. This means there are always and will always be some people who create a certain amount of abuse or trouble. On the long run, the external IP every OpenVPN user gets assigned is prohibited from editing Wikipedia, it might be banned by e-gold and on some popular webforums, one-click-hosters, etc. Not a pleasant experience for the 97% of our customers who use our service responsibly and legitimately to regain their privacy.

So even if I could change the assigned external IP every few months; e. g. from 216.xx.xx.164 to 216.xx.xx.170, it would help us a lot to combat this abuse and to provide our paying clients with "fresh" IP addresses that aren't banned or restricted on some popular Internet sites and services, yet.

Does anybody know how to change the first IP address assigned to the public interface in CentOS? So that e.g. OpenVPN in future doesn't give our OpenVPN clients the external IP 123.xx.xx.164 but rather 123.xx.xx.170?

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i don't really know how your routing looks like but i guess at the exit point you can set simple SNATing rules on ipfilter telling which source ip address should be used for outgoing [ from the vpn tunnels ] connections.

something simple as:

iptables -t nat -A POSTROUTING -s -j SNAT --to 123.x.x.170

can do the trick. i assume is a range of source ips assigned to vpn clients.

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