I have multiple 3G USB based Modems. I would like them to keep connected simultaneously, NOT necessarily aggregating their bandwidth; a separate intelligent application would manage their utilization effectively.

However I am running into problem of setting up proper routes for the ppp0,ppp1 interfaces: when one of them connects, other's entries in the routing table get updated so it is no more usable. If I reconnect the second one, it would override the first one's routing entries. If I do it over and over, sometimes both of them's entries disappear while in rare cases the two work well.

I have tried it both using NetworkManager as well as WVDial but issue pops up in both of these. Perhaps both of them use same PPP dialer at the backend and thats why this issue appears.

What is the proper solution to make them work together? In the long run, I'd also like them to automatically dial in once USB gets connected.