On Thu, 13 Oct 2016, Rogier Wolff wrote:

No! Not a "more reasonable" value! An outrageous value!

You have a network where 5 hops-in-a-row don't conform to IP standards. And
then you expect mtr to work?

traceroute works fine, ping works fine, tcp connections work fine ... but mtr is special and should fail just because the network doesn't meet your ideals? And yeah, MTR would work fine in this case if it didn't decide to give up "just because". The "give up after 5" is the /only/ thing preventing it from working properly.

To put a concrete example to it, consider the case of tunnels, esp. VPNs. It is common for the TTL of the tunneled packet to be copied to the outer packet for various good reasons. But this means that traceroute through that tunnel will not return the errors for any TTL value that causes the packet to be dropped at points between the endpoints of the tunnel, because the error will be returned back to the tunnel endpoint, not the original sender.

Happens with OpenVPN (it's even in their FAQ I think), happens with the Cisco IPSEC site-to-site tunnel used at my employer.

"Reality is that which, when you stop believing in it, doesn't go away".
                -- Philip K. Dick
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