Force data packet out a specific interface?

Is it possible to send a data packet out a specific ethernet interface?

I'm trying to troubleshoot an intermittent connectivity problem with a
server I'm hosting on eth2 of my Debian machine. It looks like my ISP is
forgetting the route to my dynamic IP address if no data is seen for 10

I'd like to set something up to do a PING out eth2 on a regular basis.