Routing public packets to private pc

(IP addresses are bogus) I have private network PC 10.0.1.15 with gateway router Cisco 1600 10.0.1.1 connected over 56k WAN link to Cisco 1600 10.0.0.150 which is on network connected to internet via Cisco 2600 T1 router 10.0.0.1 / 216.251.125.129.Cisco 2600 216.251.125.129 is configured to forward all packets addressed to 216.254.125.160 to 10.0.1.15. Ping of 216.254.125.160 gives reply from 10.0.0.150 ‘TTL expired in Transit’. 10.0.1.15 is pingable from either subnet on private network. How do I troubleshoot this?