Several interfaces accounting

[Sergey_Taurus]

Hi everybody!

I have two network Ethernet interfaces (ADSL and ISDN) and one local interface. In our country ADSL is cheaper than ISDN, but ISDN is more stable. So all incoming\outgoing traffic is summary of the ADSL and ISDN traffic. When I opening user accounting page I see the summary, for ex. 20Mb. How can I know, how much incoming\outgoing traffic for this user was recieved\sent by ADSL, and how much by ISDN? Is there is some kind of software than can do this?

Beforehand thank you.