LAN question

Paul Newell pnewell at cs.cmu.edu
Mon Sep 22 00:18:27 UTC 2008


Joel Rees wrote:
>
> On Sep 15, 2008, at 1:56 PM, Paul Newell wrote:
>
>> Fedora:
>>
>> Before I switched to F9, all my FC5 machines were happily chatting 
>> with each other through a Linksys WRT54GL but none of them could see 
>> the net.
>
> How did you set this up originally? Apparently not DHCP, from what 
> you've written about /etc/hosts, but what machine(s) did you specify 
> as the name server(s)?
>
>> I upgraded one of them to F9 and it sees the net and can ssh to the 
>> others.
>
> So, when you upgraded the one, you probably gave the install script a 
> DNS server address or two?
>
>> But the other two machines can no longer ssh into it F9 system.
>
> And I must admit, based on the /etc/hosts below, that I'm wondering 
> how you did before. ssh to a numerical IP address, perhaps?
>
>> I tried to play with things to fix it, but the best I could do was 
>> kill the network connection so that the F9 system can't see the other 
>> machine or the net. In other words, I screwed up. Since I can't 
>> figure out how to get the network back alive by restoring prior 
>> conditions, I am resigned to yet another re-install (the price of 
>> learning is lots of starting over...)
>
> If it's a slow machine, I hope you haven't already started. Waste a 
> good learning opportunity.
>
> Did you backup /etc/hosts before the upgrade, by the way?
>
>> That being said, I was hoping to get a bit of advice.
>>
>> The following is the F9 /etc/hosts file after 1) a fresh install of 
>> f9 and 2) my additions (noted with comments):
>>
>>    # Do not remove the following line, or various programs
>>    # that require network functionality will fail.
>>    127.0.0.1        chowder.localdomain chowder localhost.localdomain
>>    localhost chowder
>
> Any reason to have chowder in there twice?
>
>>    ::1        localhost6.localdomain6 localhost6
>>
>>    #-# 14sep08 (paul): self
>>    192.168.2.11    chowder
>
> I usually don't put this line in, just leave the declaration with 
> localhost to take care of it.
>
>>    #-# 14sep08 (paul): other machines available
>>    192.168.2.10    chalupa
>>    192.168.2.12    parsnip
>>
>> The next section is from one of the FC5 machines:
>>
>>    # Do not remove the following line, or various programs
>>    # that require network functionality will fail.
>>    127.0.0.1    localhost.localdomain    localhost
>>
>>    #-# self
>>    192.168.2.12    parsnip
>
> I would have put that up there on 127.0.0.1 like you did with chowder.
>
>>    #-# other machines available
>>    192.168.2.10    chalupa      192.168.2.11    chowder
>
> Should we assume that somehow two lines got combined when you pasted 
> that here, or is this the reason parsnip can't see chowder?
>
> If that's one line in your hosts file, I'm pretty sure it would 
> prevent parsnip from seeing chowder. In fact, it would likely make 
> strange things happen, like mapping "192.168.2.11" (as a string) and 
> "chowder" to to 192.168.2.10 along with chalupa. Just for parsnip, of 
> course.
>
>> I am suspect of the "localdomain" in the F9 version, but trying to 
>> play with that is what killed network (LAN and internet) ability.
>
> Hmm. What was the 127.0.0.1 line when chowder was seeing the internet? 
> And did you specify any dns servers when you set up chowder?
>
>> I went through the system->admin->network stuff and couldn't see 
>> anything that looked wrong (then again, do I know what is right?)
>>
>> As always, suggestions appreciated (including general pointers as to 
>> where to go online to learn more about all this)
>>
>> Thanks,
>> Paul
>
> [...]
>
>> I did want to add the following in case it makes any difference in 
>> your advice. My plan is to convert all the FC5 machines to F9 once I 
>> am confident in the F9 machine and my understanding of it. None of 
>> the machines are servers, they are three independent workstations 
>> that just need to ssh/scp/"s-etc" to each other. I would hope that 
>> each could independently access the internet and each other.
>
> Have you got a file in /etc/sysconfig/network-scripts called 
> ifcfg-eth0 or something similar? (ifcfg-something-other-than-lo)
>
> Does it look something like this:
> -----------------------------------
> DEVICE=eth0
> BOOTPROTO=none
> BROADCAST=192.168.2.255
> # HWADDR is your NIC's MAC address, six bytes in hexadecimal
> HWADDR=00:0e:3a:b2:51:fc
> IPADDR=192.168.2.11
> NETMASK=255.255.255.0
> NETWORK=192.168.2.0
> ONBOOT=yes
> DNS1=<your-isp-dns-server-1>
> DNS2=<your-isp-dns-server-2>
> # I don't remember what SEARCH is set to by default, maybe "localdomain"?
> # (In my case it is the domain name I get from dyndns.com.)
> SEARCH="localdomain"
> # This next line was giving me trouble earlier because I had left it no,
> # but was using network manager:
> NM_CONTROLLED=yes
> # GATEWAY would be the IP address of your Linksys.
> GATEWAY=192.168.2.1
> TYPE=Ethernet
> # I'm not sure what USERCTL and PEERDNS do at this point.
> USERCTL=no
> PEERDNS=yes
> IPV6INIT=no
> ------------------------------------
>
> That file is used by the startup scripts when they call ifconfig to 
> bring your NICs up, as I understand it.
>
> Here's a page that will tell you more:
>
> http://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/ref-guide/s1-networkscripts-interfaces.html 
>
>
> (And I think I'll go review it, myself.)
>
> Joel Rees
>
Joel:

First, as mentioned in a reply to Arthur, I've got a confirm that the 
issue is my inability to give the F9 machine a static IP w/ name as I 
can ssh in from other machines if I ifconfig the F9 machine to see its DHCP.

When I did the original install, I gave (on the network page):

network devices: left at default
hostname: chowder.localdomain
gateway: 192.168.2.2
primary DNS: empty
secondary DNS: empty

This ended up giving me network access, no sense of local static IP, a 
primary DNS resolved back to198.168.1.1 and the Gateway of 
myhome.westell.com.

I then tried a new install in which I changed the default network 
devices settings to:

(checked) enable IPv4 support
(not checked) DHCP
(checked) manual config with 192.168.2.11 / 255.255.255.0
(enable) IPv6 support
(checked) neighbor discovery
(not checked) DHCPv6
(not checked) manual config

This produced a broken network that I could never get working and nobody 
could ssh into the machine as well.

In the original FC5 setup, I could ssh via the machine's HOSTNAME or its 
static IP. I did backup the original /etc/hosts and included them in my 
last post to Arthur, plus the new F9 version after re-installing the 
original "default" way so I at least had the network working.

No way around re-installing, it seems that once I get in a bad state I 
can't undo it due to lack of knowledge. For the manual config, I did the 
reinstall(s) and didn't bother doing yum update as I just wanted to see 
if network would work. Once I went back to original default, did proper 
install.

Regarding your question of having chowder in the 127.0.0.1 line, this is 
how F9 install created the file.

Your comments of not adding the 192.168.2.11 references to self make 
sense, except I am now pretty certain my problem is that I can't tell 
the F9 box that it is "chowder" and it has a static IP of 192.168.2.11. 
I thought this info went into /etc/hosts (???)

Correct on typo for cut-and-paste of parsnip, apologies.

Regarding the ifcfg-eth0, I am attaching the file and as you can see it 
is nowhere near what you thought it might look like and clearly 
indicates that I am DHCP and my issue is learning how to make the 
machine a static IP. I considered trying to cut-and-paste your version 
in to see what happened, but I felt like that could be a 
newbie-hurts-self exercise as I have no idea what other settings might 
be assuming the old version.

I read the link you provided, read it again, then read it again. Sure 
makes it seem like I should be able to cut-and-paste, but I'm still 
trying to understand parts of the info as I am wary of parroting 
something I don't really understand. I get the DHCP versus the page's 
notes on "system using a fixed address" (8.2.1), but the other sections 
are confusing and I can't tell if they apply or not to my situation.

Wondering if I ought to convert another one of the FC5 machines to F9 
with a manual config w/ address and see if I can figure out (probably 
includes asking for help (smile) to get closer to the ifcfg you 
suggested (keeping chowder in its current state so I at least have a 
usable machine that I can begin exercising and reinstalling backed up 
personal stuff so I can start using it ... plus have web access for the 
link you gave me as right now the Linux is in one room on one floor and, 
unless it has internet, I have to go to my Windows box in another room 
on another floor and that just a lousy way to work!)

Sorry for the delay in getting back, I can only work on this stuff over 
the weekend. Suggestions appreciated.

Thanks,
Paul


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