cco is your friend. 
here are the instructions for upgrading your modem.  serial and tftp.
you actually run the tftp server on the modem. 

http://www.cisco.com/univercd/cc/td/doc/product/dsl_prod/c600s/cbos/cbo230rn.htm#xtocid2270219

having the serial upgrade procedure on hand is a good thing too.  

alternatively, Q has a gui based tool for upgrading the c67x family
that you can download from their web site.  this includes the latest
version of code.  2.4.3.

when last we saw our hero (Friday, Aug 16, 2002), 
 Michael D. Cassano was madly tapping out:
> Last night I saw a release note from the 2.4.2 version of the OS and it said
> it fixed a flaw in 2.4.1 (which I have) where the SNMP agent would send
> zeroes for several OIDs.  Ok, so that's my problem and I've downloaded
> version 2.4.2.  I don't have a means of connecting a serial cable and
> upgrading through the management port.  Anyone have any hints on how to do
> it through TFTP?
> 
> I know TFTP is insecure so I wouldn't run it long, but do I do the
> following...
> 
> Turn on a TFTP server on a linux box that has the version image
> Login to the cisco modem through telnet and run TFTP pointing at my linux
> box.
> 
> Is that all I need to do?
> 
> Mike
> ----- Original Message -----
> From: "steve ulrich" <sulrich at botwerks.org>
> To: <tclug-list at mn-linux.org>
> Sent: Friday, August 16, 2002 11:37 AM
> Subject: Re: [TCLUG] Cisco 67x question SNMP/MRTG question
> 
> 
> > no - the c67x family doesn't support snmpv3.  not a whole lot of
> > devices do actually unless there's well a defined need for the
> > partitioning capability that SNMPv3 provides.
> >
> > there were several bugs with the SNMP support in cbos.  i don't know
> > if these have been resolved in the latest release.  you might want to
> > consult the errata/release notes for the rev of code you're running
> >
> > when last we saw our hero (Thursday, Aug 15, 2002),
> >  Michael D. Cassano was madly tapping out:
> > > Hello group,
> > >
> > > I've got two routers in two different locations, one is a Cisco 678
> > > and one is a Cisco 675.  They both have built in SNMP (of course)
> > > and I'm trying to track their usage with MRTG on a linux box.  I am
> > > successfully tracking several boxes but the Cisco routers always
> > > return zeros for their traffic which I know is inaccurate.  I can
> > > snmpwalk them just fine, but MRTG can't get their traffic data in.
> > > Does it have anything to do with SNMPv3?
> > >
> >
> > --
> > steve ulrich                       sulrich at botwerks.org
> > PGP: 8D0B 0EE9 E700 A6CF ABA7  AE5F 4FD4 07C9 133B FAFC
> > _______________________________________________
> > Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul,
> Minnesota
> > http://www.mn-linux.org
> > tclug-list at mn-linux.org
> > https://mailman.mn-linux.org/mailman/listinfo/tclug-list
> >
> 
> _______________________________________________
> Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, Minnesota
> http://www.mn-linux.org
> tclug-list at mn-linux.org
> https://mailman.mn-linux.org/mailman/listinfo/tclug-list
> 

-- 
steve ulrich                       sulrich at botwerks.org
PGP: 8D0B 0EE9 E700 A6CF ABA7  AE5F 4FD4 07C9 133B FAFC