I'm running traceroute from local CE router to remote CE router thru ISP MPLS VPN in the same VPN. I assume that my ISP has 'no mpls ttl propagation'.1 10.0.5.133 0 msec 0 msec 4 msec 2 10.0.1.153 [AS 65000] [MPLS: Label 1420 Exp 0] 8 msec 4 msec 0 msec 3 10.0.1.154 [AS 65000] 8 msec * 8 msec
10.0.1.153 - ISP10.0.1.154 - Serial0 - remote CE router
Question: Why in the traceroute output the second hop is the IP address (10.0.1.153) of the outgoing interface which interconnects my remote CE to ISP (10.0.1.152/30 subnet)?
I would expect to see some interface faced towards local CE from MPLS cloud. What is the theory behind it that the ISP router is sourcing the ICMP ttl exceeded message with mentioned IP address?