To determine the path from the loopback interface on Router CE1 to the VPN interfaces on Router PE1, use the traceroute command:
user@vpn4> traceroute 192.168.192.1
source 10.255.10.4
traceroute to 192.168.192.1 (192.168.192.1) from 10.255.10.4, 30 hops max, 40 byte packets 1 vpn1-fe-110.isp-core.net (192.168.192.1) 0.828 ms 0.657 ms 1.972 ms