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@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@cs.uoregon.edu] Received: Freitag, 11 März 2016, 1:26 To: nanog@nanog.org [nanog@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)