[sf-lug] tcptraceroute, traceroute, Westell, ... Got router? / Where *is* that ("other") router? (linuxmafia.com)

[Michael Paoli]

tcptraceroute ... traceroute ...

Newer versions of traceroute - at least for (most) Linux distributions,
have doing traceroute using TCP as a built-in capability,
most notably take a look at the -T and -p (for port) options.

So, in that regard, tcptraceroute has essentially been superceded by
newer functionality of traceroute.

Even MacOS has a traceroute that can do that (or so its man page
claims) ... though "of course" it has quite different syntax.

In any case, doing a [tcp]traceroute, using TCP, and to specific
target port can be highly useful ... most notably firewalls -
often only specific traffic is allowed through the firewall(s), and
other traffic is blocked or dropped - so doing the trace with TCP
(or UDP, if that's what's used for the service of interest) and to
the applicable target port of the service, can be more useful and
informative than a more typical traceroute (UDP, high numbered sequence of
ports - the default behavior).

Westell - I still have two such ADSL "modems", same model, slightly
different firmware versions ... one I'd upgraded, one I left with the
version it had on it.  Both suffer from occasional issue - typically
about once a month or so - on average, that goes about like this (from
typical log entry):
2018-06-08
lost Internet IP connectivity over DSL
DSL modem shows three solid green lights on top
unable to ping router IP 198.144.194.233
power cycled DSL modem - this corrected the problem

Let's see ... which ones have I got ...
(again, ye olde log file of mine) ...
WESTELL , INC. MODEL : B90 - 36R516 REV : G S/N 00ST05163539
WESTELL , INC. MODEL : B90 - 36R516 REV : E S/N 00B404282008

Never know exactly when they'll fail, ... but doing a pre-emptive
power cycling of them (I sometimes do that), seems to either put the
problem off some fair while, or at least *seems to* make it less probable
to occur relatively soon after.  But not sure I've captured enough data
(nor care to?) to fully statistically analyze that.

I likely have some of the applicable firmware files ... *somewhere*.
I'm sure it's designed to be updated with (ugh) Microsoft Windows,
... but there must also be other ways.  :-)

So, yes, I have a spare ... but good to have backup(s)/redundancy ...
sometimes I swap 'em out (or loan one out - have done that at least once
thus far).
I do have (at least?) one other ADSL "modem" ... haven't tested it as
rigorously, so don't know if it's more (or less) reliable, etc.

> From: "Rick Moen" <rick at linuxmafia.com>
> Subject: Re: [sf-lug] Got router? / Where *is* that ("other")  
> router? (linuxmafia.com)
> Date: Thu, 25 Oct 2018 18:12:22 -0700

> Quoting Michael Paoli (Michael.Paoli at cal.berkeley.edu):
>
>> So, I noticed earlier, when linuxmafia.com had bit earlier been ungraciously
>> disconnected from the Internet by AT&T ...
>>
>> When I did a traceroute from my host(s) at home,
>> I only saw one hop beyond host itself.
> [...]
>
> Thanks for the probing results.  I've been meaning to do some
> poking around too, but haven't had a chance, yet.  (There's a lot of
> correspondence to do, for one thing.)  tcptraceroute might be more
> enlightening:  Sometimes, devices have been configured to not
> respond to ICMP echo on some dumb 'How to not be seen' theory
> (cue Monty Python skit).
>
> Among the things I am contemplating is a cross-check to see whether
> my 16-year-old Westell ADSL bridge device has a hardware fault or
> not.  The earlier surmise to that effect is logically open to
> question.
>
> _Or_ I could just decide it doesn't matter, and discard it.