I have a problem for which I can't give any explanation to myself. Here's what I have:
10.0.0.0 || CE_WEST -- PE_WEST -- P-SP -- PE_EAST -- CE_EAST || 22.214.171.124
I deployed an MPLS VPN between the two sites.
I read in the MPLS and VPN Architectures vol II the following:
When TTL propagation is disabled in an MPLS VPN backbone, a user who executes a
trace on a CE router will usually not see the egress PE router because that router
performs only a label lookup and is not affected with the IP TTL
I disabled TTL propagation and did a trace from 10.0.0.1 to 126.96.36.199 (CE router interfaces) and I saw PE_WEST, PE_EAST and CE_EAST in the trace, which is not what I expected to see. In the LFIB of PE_EAST, a packet to 188.8.131.52 should not trigger a L3 lookup since this network is not directly connected and is not an aggregate and thus this router should not examine the TTL field of the packet at all. I executed a few debugs on the routers and noticed that PE_EAST does not do any L3 lookup. However, I see it in the trace and can't find an explanation for this.
Maybe I did not understand something or it's just something that has changed over time in recent IOS version(let's not forget the book is from 2003).
Any ideas why this happens will be very much appreciated.
The behavior described in your original post used to be true but has since been changed as of 12.3(13), 12.0(31)S, 12.2(18)SXE and 12.3(14)T.
Hope this helps,