[j-nsp] traceroute in mpls vpn's not showing P hops

[Skyler Blumer]

There's a knob called icmp tunneling. P routers push the TTL expired 
messages along the LSP to the egress PE, which has a route back to the 
source CE in its VRF.


On 8/22/17 9:39 PM, Aaron Gould wrote:
> I know that this is a known thing with mpls networks, and there are a few
> tricks with no decrement ttl or no propagate ttl to cause P cloud to be
> completely invisible. but is there a way to do the opposite?...that is, is
> there a way to cause the P routers to be seen on traceroute ?  I understand
> that ttl expired in transit messages need to be able to be sent back to the
> CE that sent the low-ttl packets to begin with and since p router probably
> won't have the vrf-specific routes of that ce, then, well.. I guess I'm
> wondering if there's some trick command that allows the p router to send
> back the ttl-expired-in-transit messages simply via the same mpls label
> values via the lsp that they arrived on. or whoever it would work. ?
>
>   
>
> ----- trace initiated be CE r1
>
>   
>
> r1 at lab-mx104:r1> traceroute 1.1.10.2 wait 1
>
> traceroute to 1.1.10.2 (1.1.10.2), 30 hops max, 40 byte packets
>
> 1  1.1.0.2 (1.1.0.2)  0.539 ms  0.646 ms  0.472 ms               <---- PE
>
>   2  * * *
> <---- P
>
> 3  * * *
> <---- P
>
> 4  * * *
> <---- P
>
> 5  * * *
> <---- P
>
> 6  * * *
> <---- P
>
> 7  1.1.10.1 (1.1.10.1)  0.611 ms  0.565 ms  0.534 ms           <---- PE
>
> 8  1.1.10.2 (1.1.10.2)  0.569 ms  0.616 ms  0.700 ms           <---- CE
>
>   
>
> - Aaron Gould
>
>   
>
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