Short-circuited traceroutes on FIOS

[rwf at loonybin.net (Rob Foehl)]

On Tue, 10 Dec 2019, Joe Maimon wrote:

> Anyone have an idea why there are some destinations that on residential 
> verizon fios here in NY area terminate right on first external hop?

They're returning fake ICMP echo replies from their BNGs for echo packets 
with TTL=1, thus any ICMP traceroute (Windows and mtr by default, etc.) 
seems to terminate at their layer 3 edge.  UDP/TCP traceroute are 
unaffected, ICMP works fine if you set the initial TTL to n+1 where n is 
the hop that's lying.

Support claims that it was a mistake, but it's also been 15+ months and 
it's pretty deliberate behavior.  Draw your own conclusions...

-Rob