I've had a tertiary Ubuntu box for some time that couldn't access the public gateway, but did fine private. I finally decide to see why, and realized I had enabled the 2nd NIC some time back for a specific job, now not needed. Suspecting this conflict, I ran "ifconfig eth1 down." And sure enough, I could hit the public fine. However, it came back as I pinged it from another box -- even though I had removed it from "interfaces" under /etc/network.

I even restarted networking with "/etc/init.d/networking restart" and it still comes back.

Please explain. Is it caching the information now removed from interfaces?