Something is Fishy About My Network

Kevin J. Cummings cummings at kjchome.homeip.net
Thu Mar 5 02:23:34 UTC 2009


Marc Ferguson wrote:
> Hi,
> 
> I'm running Fedora 10 x86_64 and I really think something is odd about 
> my ability to network and I think it's all pointing to DNS.  First, I've 
> been running Linux (full time) for almost a year, but I am still a 
> newb.  There are still some Windows concepts that I haven't been able to 
> shake yet, so please be very simple yet thorough with your replies (I'd 
> appreciate it).

Look at the guidelines link at the bottom of each email you receive.
It suggests that you don't post in HTML to this list.

> 
> So here's the meat of my cry-for-help caserole. 
> 
>     * I'm having a problem pinging my hostname.  I'll ping it and
>       127.0.0.1 is the resulting IP.

Look at your /etc/hosts file.  Odds are, your hostname is attached to 
your loopback device address.

>     * I see that my router has given my computer an IP address, but it
>       doesn't have the hostname in its table.

That's the second half of the equation.  If you are getting an IP 
address from your router, your router probably has NO WAY to update 
whatever DNS is looking at, and it certainly can't update your 
/etc/hosts file for you.

>     * I can't ping, by host name, my computer from any other computer on
>       the home network.

Because they have no way to know what address your router gave it or 
what name is associated with your computer's IP address.

> So because of those issues, I can't properly network my linux box with 
> other computers in my home network.  I just found out (from a friend) 
> that I had an internal firewall turned on.  I didn't even realize that 
> Fedora shipped with a firewall.  From my Windows-days, I've learned that 
> software firewall causes too many headaches.  So; I disabled the 
> firewall I discovered in Fedora.  Thanks for any feedback.

Bad idea unless you know what you are doing, but your firewall is not 
the problem here.

> _*system-config-network 1.5.95*_
> I'm not all that handy with command-line network configuring yet so I'm 
> using the GUI program system-config-network.  In my DNS tab here are my 
> settings:
> 
>     * hostname: unicron.cybertron
>     * primary dns: 192.168.1.1 (router)
>     * secondary dns:
>     * tertiary dns:
>     * dns search path: unicron

These fields (except maybe the hostname) are all set by your DHCP server 
(in this case, your router).

Suggestion #1:  Use a static IP address in your network that your router 
will not allocate.  Then you can add it to each machine's /etc/hosts file.

Suggestion #2 (if you are up to it):  Disable DHCP serving in your 
router and setup a DHCP server on a Linux machine.  You can set up the 
dchp.conf file to do everything your touter is doing.  If this machine 
is also running DNS, there are some ways to get them to talk to each 
other so that DNS knows the names of machines served by the DHCP server.
This is not trivial, and requires in depth knowledge of both protocols 
to get to work right.  Possibly including depricated configuration options.

Suggestion #3 (the cheap way out):  Figure out what IP addresses are 
allocated by your router and manually add them to your machines 
/etc/hosts files.  If they change, you'll be responsible for keeping 
/etc/hosts up-to-date.

-- 
Kevin J. Cummings
kjchome at rcn.com
cummings at kjchome.homeip.net
cummings at kjc386.framingham.ma.us
Registered Linux User #1232 (http://counter.li.org)




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