On 02/02/2012 11:28 AM, Nick wrote: > And if it isn't, is there anything I should bear in mind when hacking a script > to do this sort of thing, in order to avoid breaking my system or generally > fighting against the system's assumptions? > I would have ping the gateway of primary link (maybe both) and some outside IP on that path, and in case of timeouts I would activate changes or something. Like "heartbeat" tests. But I recommend you read: http://www.shorewall.net/Shorewall_and_Routing.html and then consider using shorewall in MultiISP environment. I do not think Basic routing is able to deal with changing circumstances, at least not fast enough. One solution would be running dynamic routing protocols, like OSPF or OLSR, which involves running then on several routers/systems, or using some active script like shorewall. -- Ljubomir Ljubojevic (Love is in the Air) PL Computers Serbia, Europe Google is the Mother, Google is the Father, and traceroute is your trusty Spiderman... StarOS, Mikrotik and CentOS/RHEL/Linux consultant