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Tracert - Do Routers implement look ahead for failed sites?

wisty
Aspiring Pro
Posts: 431
Thanks: 53
Fixes: 3
Registered: 30-07-2007

Tracert - Do Routers implement look ahead for failed sites?

On Saturday the University of Reading had a (planned) major electrical outage which took down almost all the network services. During the outage (I had not seen the notification ) I attempted to diagnose why I couldn't reach the site.

A Tracert failed at the second hop (i.e at the Plusnet gateway) and gave me

#1 ADSL (10.0.0.10): TTL Exceeded, ttl=255, 0 ms
#2 lo0-plusnet.pte-ag1.plus.net (195.166.128.64): TTL Exceeded, ttl=126, 31 ms
#3 *

which I (mis) diagnosed as a Plusnet routing problem.
Today (with the University back up) I get

#1 ADSL (10.0.0.10): TTL Exceeded, ttl=255, 0 ms
#2 lo0-plusnet.pte-ag1.plus.net (195.166.128.64): TTL Exceeded, ttl=126, 31 ms
#3 ge0-0-0-403.pte-gw1.plus.net (84.92.4.1): TTL Exceeded, ttl=252, 15 ms
#4 ge0-0-0-22.ptn-gw1.plus.net (212.159.4.1): TTL Exceeded, ttl=251, 16 ms
#5 gi1-1-22.ptn-gw5.plus.net (212.159.4.6): TTL Exceeded, ttl=251, 16 ms
#6 linx-gw2.ja.net (195.66.226.15): TTL Exceeded, ttl=250, 31 ms
#7 po2-0.lond-scr3.ja.net (146.97.35.249): TTL Exceeded, ttl=249, 31 ms
#8 po0-0.read-scr.ja.net (146.97.33.3Cool: TTL Exceeded, ttl=248, 32 ms
#9 po2-0.reading-bar.ja.net (146.97.35.7Cool: TTL Exceeded, ttl=247, 31 ms
#10 Unavailable (146.97.40.70): TTL Exceeded, ttl=119, 31 ms
#11 ge-3-1.fw-ext.rdg.ac.uk (134.225.254.1Cool: TTL Exceeded, ttl=54, 31 ms
#12 webmail-slb.rdg.ac.uk (134.225.1.45): Echo Reply, ttl=117, 31 ms

I thought that the Saturday Tracert would have reported back as far as as Janet (say hop #7) or do Plusnets gateways have some form of intelligence that tracks and kills traffic to sites that are "known" to be down?

Can anyone enlighten me - my knowledge of the tracert process appears to be broken.