I think I got it!

I changed the ping servers, put googleDNS and openDNS, restarted syswatch (the logs show it failed and sometimes it passed the ping server check on both servers)...

Then I tried pinging google using eth2, it started pinging but loosing packets for moments, then pinging again, so I changed the cable as Tony suggested on 1) and boila! the pinging was permanent! So maybe the cable was faulty?

The thing that confuses me is how it worked on pppoe and the modem on bridge mode?

But nonetheless, it is working now!

Thank you Tony, Duncan and Nick for your support, I am sincerely grateful!