Your right - it’s a broken L2. Only routers are supposed to decrement TTLs. Links and tunnels themselves aren’t. Joe > On Dec 6, 2018, at 5:16 AM, Stewart Bryant <stewart.bryant@xxxxxxxxx> wrote: > > > >> On 06/12/2018 05:22, Joe Touch wrote: >> >>> On Dec 5, 2018, at 9:01 PM, Christopher Morrow <morrowc.lists@xxxxxxxxx> wrote: >>> >>> How is it, for example, different to put ipv6 packets into an MPLS path doing nothing along 'many' hops (except forwarding the packets along), and then once you pop out of the tunnel start processing the packet as you (joe) would want. >> The hopcount doesn’t get decremented by L2. >> >> Joe > > MPLS is not L2. > > MPLS has two modes, one in which the TTL of the IP payload is decremented on ingress and the TTL across the MPLS path is ignored. In the other mode, the TTL of the IP packet minus one is copied into the MPLS label which is then decremented as the packet travels across the network at egress from the MPLS layer the TTL is copied back into the the IP packet. > > - Stewart
