> I have been having problem with traffic to port 153 keeping > the PPP0 link > up. > I am using iptables to try and filter out (DROP0)this traffic > in the INPUT, > FORWARD and OUTPUT chains, but can't get it to work. You need to use the filtering mechanism in pppd rather than IPtables to determine what traffic should be regarded as valid traffic which should keep the link up. This is because pppd sees all the traffic before it makes its way to netfilter. Regards, John