Problem with trunk

Hy, i’m beginner in asterisk, and in my company i have installed asterisk, and it works very vel, excelent. But sometimes, my iax trunk goes down, ureacheable. I’m using dyndns.

I would like to make cron job on centops and check every 15 minutes is my iax trunk up. Please couly someone help me.

I’v red everthing about cron job on linux, but i don’t know how use it with asterisk.

Best regards!