I know I have already asked this question previously and not been able to find out an answer, as I was not able to narrow down the issue that was triggering this problem.
However now I am certain that the issue is with the router itself (Draytek 2830). As when the internet goes offline for about few seconds and comes back online, the trunks go unreachable and never come back on. The simple resolution to this issue I have found is to reboot the router and the trunks come back online. Anyone with any idea what could be the problem.
I have already disabled the SIP Alg on the router. The router is on static public IP with BT and my Asterisk box is on static private IP. The machine is port binded to 5080 and this port is pointing/forwarded to my Asterisk IP in the router. Also I have enabled the 10k to 20k RTP ports on the router.
Any help/pointers would be appreciated.