Re: Help interpret a strange traceroute?

[Dovid Bender <dovid () telecurve com>]

Does anyone have an IP that involves a load balancing router to test with?



On Mon, Oct 31, 2016 at 5:54 PM, Bryan Holloway <bryan () shout net> wrote:

> On 10/31/16 4:20 PM, Olivier Benghozi wrote:
>
> > Hi Randy,
> >
> >
> > ECMP loadbalancing is most frequently done on layer3+layer4 headers, and
> > unixlike traceroute use UDP with increasing destination port number for
> > each packet (usually starting at 33434), which allows to see the different
> > available paths, as wrote William.
> >
> > Would you want/need to stick to only one traceroute path, you may use
> > ICMP traceroute instead of UDP traceroute (no port in ICMP, so only layer 3
> > available to loadbalance, so all packets will go through the same
> > interface).
> >
> > Usually it is achieved by using traceroute -I yourdest
> > Windows tracert is ICMP only traceroute by the way. MTR tool is also ICMP
> > based by default.
> >
> > Keep in mind that it looses some useful information, though (since you
> > see only one path and don't decide which).
> > So, you can also use UDP traceroute with fixed port (by example 33434
> > with no port increase), and try again the same traceroute with another
> > destport (with fixed port too, by example 33435), which would display two
> > different paths in a more readable way. RTFM is required since the options
> > depend on your traceroute particular specie :)
> >
> >
> > Olivier
> >
> > On 31 oct. 2016 à 20:42, William Herrin <bill () herrin us> wrote :
> > > On Mon, Oct 31, 2016 at 3:33 PM, Randy <amps () djlab com> wrote:
> > >
> > > > Any idea how a traceroute (into my network) could end up this fubar'd?
> > > > Discovered this wierd routing while investigating horrendously slow
> > > > speeds
> > > > (albeit no packet loss) to a particular ISP abroad.
> > >
> > > Hi Randy,
> > >
> > > This is per-packet load balancing. In the forward path the alternates
> > > are different lengths but the traceroute stops as soon as at least one
> > > of the paths reaches the destination.
> > >
> > > The return path is also engaged in per-packet load balancing but the
> > > paths are all the same length.
> This is also a handy tool that addresses the same issues:
>
> https://paris-traceroute.net/