[lug] Hostname, Knoppix, where does it come from?

Bob Collins bcollins at peakpeak.com
Thu Jun 29 21:13:53 MDT 2006

Nate Duehr wrote:
> On Jun 28, 2006, at 8:42 PM, Bob Collins wrote:
>> Ed Moxley wrote:
>>> On Wed, 2006-06-28 at 17:06, Bob Collins wrote:
>>>> I decided to install a fresh version of SuSE 10.0. Everything went 
>>>> fine except that this is what I get when I ping from another 
>>>> computer on my local network. bob at matt:~> ping linux.local PING 
>>>> linux.local ( 56(84) bytes of data. 64 bytes from 
>>>> Knoppix ( icmp_seq=1 ttl=64 time=0.139 ms 64 bytes 
>>>> from Knoppix ( icmp_seq=5 ttl=64 time=0.167 ms
>>> Do you really want the box to be called linux.local? You might try 
>>> changing back to dhcp from the static config and changing the host 
>>> name to a single name like linuxwhatever (without the dot) and see 
>>> if the Knoppix name goes away.
>> Linux is not a good name for a computer box, but it has had that name 
>> for many years. All of the computers on my local area network have 
>> the the box_name.domain_name where domain_name is local. I add the 
>> .local to linux in the email because of the other meanings for linux, 
>> which makes it confusing.
>> Tech support at peakpeak.com answered my email by saying I should 
>> contact Novell/SuSE tech support. I copied another person there who 
>> seems to know a little more about linux and what is going on, but I 
>> really don't expect much help from peakpeak.com.
>> I should have checked them out a little better, but I am sure they 
>> are not as bad as msm.com, the Qwest default internet provider.
>> Thank you all for your help.
>> Bob
> Bob,
> Here's my 3AM comments.  Hope they're not too rambling and make at 
> least a little sense to you after posting at this horrible hour.  
> (Can't sleep.)
> From many years of experience with DNS -- and making some assumptions 
> about how your 2wire brand router works, I'd say the following happened:
> First off, your router is apparently acting as your local DNS server 
> for anything on your internal LAN subnet, and it hands out it's own IP 
> address for serving DNS requests in the initial DHCP request from your 
> clients.  (This is pretty easy to check - if all your DHCP clients 
> show your router's internal IP address as their DNS server, that's 
> what it's doing.)  MANY small router/firewalls do this nowadays to 
> make setup easy for everyone - no more setting up a DNS server in the 
> router - it just proxy's the requests.
> You booted Knoppix and its DHCP client has the relatively (many years, 
> but...) new feature turned on that not only asks the router for an 
> internal private IP address, but also sends a DNS update packet using 
> it's machine name to the router.
> Your router now believes that's the name of the machine on that 
> particular internal IP address.  It also appears that your router 
> "splits" your DNS and keeps track of machine names internally using 
> the 2wire.com domain name internally also.  (You don't own or operate 
> the 2wire.com domain and theoretically should have no possible way to 
> update/add/change it.  So assuming 2wire isn't doing some kind of free 
> dynamic DNS service for all of their routers -- which I very highly 
> doubt -- this naming phenomenon is limted to your local LAN behind the 
> 2wire router.  No one "on the Internet" can see or use any of the DNS 
> names you've mentioned from the outside world of the Internet itself.)
> Okay having worked on a couple of 2wire routers before I can say two 
> things about them.  They're set up by default to make it virtually 
> impossible for a user to screw up their Internet connectivity -- they 
> make all the "choices" you should be making for yourself about your 
> network for you.  Second, they usually have an "Advanced" mode where 
> you can override certain behaviors, but it wouldn't surprise me at all 
> if they didn't provide a way to turn this auto-DNS junk off internally.)
> So, a couple of thoughts...
> Did you try rebooting the 2wire router?  If you're lucky and they 
> don't store DHCP information in non-volatile memory (flash), perhaps 
> it'll simply "forget" it ever knew a name for that IP address after a 
> restart.
> Next, you could always turn on the same feature that Knoppix is using 
> to update DNS from your other Linux.  If Knoppix can set/change the 
> name in the router during its DHCP sessions, so can your other Linux.  
> How easy or difficult that might be is probably something you'd need 
> to research, but I'd start with Googling for "Dynamic DNS + DHCP + 
> <Distro name>" and going from there.  It's probably relatively easy to 
> tell your SuSE to do it, but I've never done it on SuSE, so I can't 
> elaborate at all.
> Finally -- the simplest question... why do you care what the 2wire 
> router calls the machine on your internal LAN?  If the early 
> assumption is correct that 2wire doesn't "publish" this name in any 
> way out to the Net, it simply doesn't matter.  You can put a hosts 
> file entry on the other machines to give that machine ten different 
> names that work that you can call it by, other than the one you don't 
> like... or you could even set up an internal DNS server if there is 
> some way to tell the 2wire NOT to hand out its own IP address as a DNS 
> server for your internal LAN.  I doubt they give you this option, the 
> 2wire routers are pretty limited, trying to make things "easier" on 
> you.  All they accomplish is making it SO easy, you don't really know 
> what's going on and missed a number of key things like learning how 
> hostnames and DNS resolve, which is pretty basic core networking 
> knowledge.
> To summarize: Don't worry about it.  Use the real IP address or add a 
> hosts file entry or two to call it what you want on your internal 
> network.  If you REALLY want to know how to straighten it out, you're 
> going to have to do the research to figure out how Knoppix set it in 
> the first place and duplicate the effort on SuSE.  Linux is Linux, so 
> it *can* be done, but it may be easy (if the feature is built-in to 
> SuSE and just not enabled) or difficult (have to find and build the 
> DHCP client Knoppix is using if your SuSE's version won't do it).
> The only other serious comment I might offer is this:  If you want to 
> learn how something like networking, routing and DHCP work, including 
> the DNS server assignment, etc... the absolute best way would be to 
> find everything labeled "Auto" in the 2wire and set it to manual -- 
> and attempt to build your network from the ground up, and get it 
> working, with all static IP's, hostnames, perhaps a DNS server... if 
> you feel like purchasing a domain name, etc... everything set up and 
> configured by YOU, not the engineer that built the 2wire router -- 
> they built it to do everything for you but butter your morning 
> toast... and it sounds like it's doing just that... anytime a computer 
> isn't doing what you want it to, do like you just did and dive in with 
> both feet and figure out why -- it's only doing what it was programmed 
> or told to do by *someone*... in this case, it certainly sounds like 
> that would be the 2wire engineers.
> It also sounds like peakpeak.com has NOTHING to do with what you're 
> seeing -- other than choose a really cheesy hard-to-configure-manually 
> router for their customers.  But I guarantee they did it to keep 
> setups simple and installation easy and to save themselves having to 
> directly support users needing assistance with network setup.
> Oh yeah, the reason your ping is even showing a name on the replies is 
> that your client doing the ping is doing a reverse DNS lookup on the 
> internal address of your linux machine.  The 2wire is just handing it 
> the name it knows about.  Changing the machine's internal address 
> could/should allow you to work from an IP that 2wire knows no 
> information about.
> Nate Duehr
> nate at natetech.com
> _______________________________________________
> Web Page:  http://lug.boulder.co.us
> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> Join us on IRC: lug.boulder.co.us port=6667 channel=#colug

Thank you for your words of wisdom. It must be the practice you had 
getting ready for finals. You seemed lucid to me. I decided to change 
the range of DHCP addresses and eliminate the old addresses. This seems 
to have fixed the problem, if you can call it a problem.

I don't think the DSL modem can forget an address and what it learns 
about it. Even if it is wrong.

As for the reason I care about it, I suppose I am more than a little 
anal retentive.

Thanks to everyone who offered help. I appreciate it.


More information about the LUG mailing list