3

When I traceroute bbc.co.uk in my home Network the first hop appears 4 times. What could be causing this ?

@Latitude-7480 ~ $ tracepath bbc.co.uk
 1?: [LOCALHOST]                                         pmtu 1300
 1:  10.87.0.1                                             1.489ms 
 1:  10.87.0.1                                            23.899ms 
 1:  10.87.0.1                                             1.631ms 
 1:  10.87.0.1                                            28.040ms 
 2:  10.255.144.0                                         34.858ms 
 3:  172.16.212.252                                       75.383ms 
 4:  145.15.245.9                                        112.480ms 
 5:  145.15.245.26                                        38.264ms asymm  4 
 6:  ns.nikhef.jointtransit.nl                            46.137ms asymm  5 
 7:  be4784.ccr21.ams04.atlas.cogentco.com                34.456ms asymm  6 
 8:  be3457.ccr41.ams03.atlas.cogentco.com                33.586ms asymm  7 

closed as off-topic by Ron Maupin Mar 15 '18 at 16:47

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "NE is a site for to ask and provide answers about professionally managed networks in a business environment. Your question falls outside the areas our community decided are on topic. Please visit the help center for more details. If you disagree with this closure, please ask on Network Engineering Meta." – Ron Maupin
If this question can be reworded to fit the rules in the help center, please edit the question.

  • Unfortunately, questions about networks that are not under your direct control are off-topic here. – Ron Maupin Mar 15 '18 at 16:47
3

This is due to path MTU discovery.

As you can see the MTU for you first hop is 1300, while you computer expect 1500 by default.

So tracepath will send several packets to determine the correct MTU, and in this case it took 4 try to get it right.

Then it continue the trace to the destination.

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