This morning the DSL was still acting up (ie., not working, with traceroute dying at random points on different routes) on many websites worldwide, including Eircom's own DSL support page (dsl-support.eircom.net) which is hosted here in Ireland. So I called up technical support and immediately they told me that the problem was that I had an "invalid IP" assigned. Apparently they have a number of these invalid IPs in the pool (for the PPPoE connections) which they are "trying to remove" and if you get one of those assigned for your dynamic IP a number of sites on the Internet will not be reachable. The solution is to turn off the modem and wait for a while... and if that doesn't work (as in my case, since I did that in the morning) call up tech support and they will release the IP and make sure that the new IP assigned will not be one of the invalid ones. Sounds weird that an IP in the pool might work for some sites and not others. I wonder what kind of routing boxes they are using.

Now, if you ask me, it shouldn't be so hard to write a little program that would check each IP in turn and remove those that don't work no? Why wait until customers complain?

Anyway, if you're in Ireland, use Eircom DSL and you have problems reaching some websites, this might be the reason.