[LINK] Yet More Strange DNS Behaviour

[Roger Clarke]

Telstra ADSL was a complete mess this afternoon.

I'm still on my fallback dial-up connection, and testing to see if 
the Telstra Support Page (which is *dreadful* HTML, but that's 
another story) is telling the truth when it says that nothing's wrong 
(and, by implication, that nothing ever *was* wrong ...).

But I get rather strange behaviour.

A traceroute to my normal SMTP server, at:
mail-hub.bigpond.net.au
implies that what I asked to speak to was:
203.18.76.88	pitt7-ispmail-r02.nsw.ipm.bigpond.com (details below)

If I do a domain-name lookup, I get:
mail-hub.bigpond.net.au = 144.135.25.13, 144.135.24.13

I assumed that:
(a)  a Mac Interarchy 4.1 domain-name lookup simply asks the DNS for the
      IP-address corresponding to the domain-name provided;  and
(b)  a Mac Interarchy 4.1 traceroute uses the DNS to look up the IP-address
      and then sends packets in that hopscotch-style pattern to successive
      nodes along the route until it gets a time-measure back from the
      target IP-address, i.e. the requested domain-name (orright, substitute
      node-name for domain-name, but if you've got this far, then you know
      what I mean).

But judging by the above data, my assumption must be wrong !?

Why does a traceroute to A return a set of data for B??



1	3/3	0.111	0.115	0.120	203.20.62.3	cisco1.apex.net.au
2	3/3	0.118	0.127	0.144	203.20.62.18
3	3/3	0.112	0.137	0.153	203.20.62.1
4	3/3	0.101	0.121	0.158	203.220.47.73
5	3/3	0.153	0.173	0.198	203.194.57.61
6	3/3	0.123	0.151	0.168	203.194.1.25 
	s3-0.cor02-kent-syd.comindico.com.au
7	3/3	0.138	0.153	0.178	203.194.1.2 
	pos3-0-0.cor01-dryb-mel.comindico.com.au
8	3/3	0.126	0.144	0.176	203.194.56.56 
	fe1-0.bdr01-dryb-mel.comindico.com.au
9	3/3	0.130	0.163	0.221	202.139.138.197 
	atm11-0-0-19.mn1.optus.net.au
10	3/3	0.135	0.144	0.159	139.130.6.25 
	pos-6-1-0.lon20.melbourne.telstra.net
11	3/3	0.127	0.182	0.260	203.50.79.129 
	gigabitethernet3-0.win-core1.melbourne.telstra.net
12	3/3	0.121	0.137	0.167	203.50.6.165 
	pos2-0.ken-core4.sydney.telstra.net
13	3/3	0.154	0.176	0.191	203.50.19.168 
	gigabitethernet1-1.chw30.sydney.telstra.net
14	3/3	0.126	0.134	0.150	139.130.7.10 
	bphcwip3.lnk.telstra.net
15		0.132	0.180	0.229	203.18.76.88 
	pitt7-ispmail-r02.nsw.ipm.bigpond.com

-- 
Roger Clarke              http://www.anu.edu.au/people/Roger.Clarke/

Xamax Consultancy Pty Ltd, 78 Sidaway St, Chapman ACT 2611 AUSTRALIA
                 Tel: +61 2 6288 1472, and 6288 6916
mailto:Roger.Clarke@xamax.com.au            http://www.xamax.com.au/

Visiting Professor, Uni of Hong Kong, Dept of Comp Sci and Info Sys
Visiting Fellow, Australian National University, Dept of Comp Sci