Figuring out traceroute

Fri Mar 11 06:07:28 UTC 2016

Looks like the device is always las-b3 (Los Angeles, border 3). As far as I know Telia works with IS-IS and multiple load balanced links from each bb (backbone) router to each border router. Usually they don't deal with L2 in case of customer BGP downlinks.

Jürgen Jaritsch
Head of Network & Infrastructure

ANEXIA Internetdienstleistungs GmbH

Telefon: +43-5-0556-300
Telefax: +43-5-0556-500

E-Mail: jj at anexia.at
Web: http://www.anexia.at

Anschrift Hauptsitz Klagenfurt: Feldkirchnerstraße 140, 9020 Klagenfurt
Geschäftsführer: Alexander Windbichler
Firmenbuch: FN 289918a | Gerichtsstand: Klagenfurt | UID-Nummer: AT U63216601

-----Original Message-----
From: Reza Motamedi [motamedi at cs.uoregon.edu]
Received: Freitag, 11 März 2016, 1:26
To: nanog at nanog.org [nanog at nanog.org]
Subject: Figuring out traceroute

Hi guys,

This might seem a bit of a trivial question, but I guess there is no harm
in asking. I am looking at a collection of traceroutes all go through the
following consecutive hops (* >> 213.248.98.238), as shown here (I kept the
DNSname just for completeness):

+ From >> To
+ (213.155.130.125:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.130.127:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.131.75:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.131.83:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.131.85:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.134.251:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.134.253:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.134.77:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.137.57:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (213.155.137.59:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.114.111:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.168:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.170:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.174:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.176:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.178:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.180:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.182:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.184:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.186:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.188:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.116.190:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.140.253:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)
+ (62.115.140.255:las-b3-link.telia.net) >> (213.248.98.238:b
harti-ic-140621-las-b3.c.telia.net)

Given the way traceroute works (most of the times), which reports back the
ingress port of the router it hits, do you think it fair to assume that all
the hops that I see on the `From` hop are all different ports of one
router? I think the other explanation is that there is switch (or something
that does not have IP footprint) between `From` side and `To` side. How
probable do you think this second explanation is?

Best Regards
Reza Motamedi (R.M)