help on network - 1
klee12
I'm running a computer where I can boot up under Suse 6.3, Windows 98,
and Slackware 10.0. My computer is connected to a Linksys
router/firewall which is connected to a cable modem. The net was
working fine until yesterday, then strange things happened (I'll give
all the details in the next post). I called user support (at my ISP and
at Linksys) and with their help I got my computer accessing the net
under Windows. They fixed the problem by switching Windows from running
with static IP address to DHCP. So I went to my 2 Linux OS's and
switched both to DHCP, and everything works OK (so far). However I'm
afraid something may break in the future
1. Do all the network related files in /etc, like hosts, resolv.conf
still work like they did before?
2. I chose as my domain name .mit.edu. I chose it because I wanted
mail to go to alum.mit.edu. Might this domain name cause problems now
with DHCP?
3. I have one other (two others when I get a new computer) computer on
my network. I use the second computer as a place to backup files, and
for my son when he comes home. How can my present computer get the IP
address of the second computer when I switch it to DHCP? I may wamt
keep the second computer with a static IP address 192.168.1.2 for the
present; might my router running DHCP give that IP address to another
computer on my net? By the way,how does one find the current IP address
under DHCP? How does one find the gateway address?
Thanks in advance. You've been great with your answers.
klee12
Simon
> I called user support (at my ISP and
> at Linksys) and with their help I got my computer accessing the net
> under Windows. They fixed the problem by switching Windows from running
> with static IP address to DHCP.
That can't have been the only problem. As long as both the router and
the machines on the network know what the addressing scheme is, you
should be fine. If your router knows your machine's static IP address,
that's one way of doing it. If it doesn't, you can get a DHCP lease
from the router.
> 1. Do all the network related files in /etc, like hosts, resolv.conf
> still work like they did before?
They do.
> 2. I chose as my domain name .mit.edu. I chose it because I wanted
> mail to go to alum.mit.edu. Might this domain name cause problems now
> with DHCP?
It shouldn't normally, but there's no reason to set that as your domain
name just to send mail to a mail server under that domain.
> 3. I have one other (two others when I get a new computer) computer on
> my network. I use the second computer as a place to backup files, and
> for my son when he comes home. How can my present computer get the IP
> address of the second computer when I switch it to DHCP?
This is one of the problems with DHCP and the main reason that I don't
use it. You could play with DNS name registration on the machines, but
that's not something I've had occasion to use.
> I may wamt keep the second computer with a static IP address
> 192.168.1.2 for the present; might my router running DHCP give that
> IP address to another computer on my net?
Yes, it may do, if it doesn't check whether an IP address is in use
before assigning it.
> By the way,how does one find the current IP address under DHCP?
ifconfig. It's the same as with static IP addresses.
> How does one find the gateway address?
route. Again, it's the same. All DHCP is is another way of giving an
IP address and routeing information to the kernel. You can then access
that information in exactly the same way.
--
Simon <si...@no-dns-yet.org.uk> **** GPG: F4A23C69
"We demand rigidly defined areas of doubt and uncertainty."
- Douglas Adams
Floyd L. Davidson
>On 19 Jan 2005 14:13:15 -0800, klee12 <kle...@alum.mit.edu> wrote:
>> I called user support (at my ISP and
>> at Linksys) and with their help I got my computer accessing the net
>> under Windows. They fixed the problem by switching Windows from running
>> with static IP address to DHCP.
>
>That can't have been the only problem. As long as both the router and
>the machines on the network know what the addressing scheme is, you
>should be fine. If your router knows your machine's static IP address,
>that's one way of doing it. If it doesn't, you can get a DHCP lease
>from the router.
That is *very* likely to be precisely the problem!
For example, the Linksys WRT54G wireless router comes with
"factor defaults" that enable DHCP, *and* only routes to the
range of addresses that DHCP will assign, which is a group of 50
starting at 192.168.1.100. Trying to access a Linksys wrt54g
out of the box, or if "factory defaults" are set by command, or
if the "reset" button is held down for 8 or more seconds, will
work if and *only* if the host accessing the router does have an
IP in that range, whether it comes from DHCP or is a static IP.
Hence, changing from a static IP, that is not routed, to DHCP
would change the IP address of the windows machine and allow it
to work.
>> 1. Do all the network related files in /etc, like hosts, resolv.conf
>> still work like they did before?
>
>They do.
>
>> 2. I chose as my domain name .mit.edu. I chose it because I wanted
>> mail to go to alum.mit.edu. Might this domain name cause problems now
>> with DHCP?
>
>It shouldn't normally, but there's no reason to set that as your domain
>name just to send mail to a mail server under that domain.
It is a *very bad* idea. Anything that looks for a domain name,
has a 50-50 chance of being wrong (depending on which was
actually wanted).
>> 3. I have one other (two others when I get a new computer) computer on
>> my network. I use the second computer as a place to backup files, and
>> for my son when he comes home. How can my present computer get the IP
>> address of the second computer when I switch it to DHCP?
>
>This is one of the problems with DHCP and the main reason that I don't
>use it. You could play with DNS name registration on the machines, but
>that's not something I've had occasion to use.
>
>> I may wamt keep the second computer with a static IP address
>> 192.168.1.2 for the present; might my router running DHCP give that
>> IP address to another computer on my net?
>
>Yes, it may do, if it doesn't check whether an IP address is in use
>before assigning it.
Check what range of addresses the router will assign. Or better
yet (IMHO), disable the DHCP server in the router and provide it
with appropriate routing table entries. It might be easy, for
example, to just give everything static addresses within the
range that the default routing table entries match. That way only
DHCP needs to be disabled, and it will still work if the defaults
get reset again.
>> By the way,how does one find the current IP address under DHCP?
>
>ifconfig. It's the same as with static IP addresses.
>
>> How does one find the gateway address?
>
>route. Again, it's the same. All DHCP is is another way of giving an
>IP address and routeing information to the kernel. You can then access
>that information in exactly the same way.
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) fl...@barrow.com
klee12
Simon wrote:
> > 2. I chose as my domain name .mit.edu. I chose it because I wanted
> > mail to go to alum.mit.edu. Might this domain name cause problems
now
> > with DHCP?
>
> It shouldn't normally, but there's no reason to set that as your
domain
> name just to send mail to a mail server under that domain.
Actually at first I set the domain to alum.mit.edu because I wanted
replies to my email to go there ... too many people were replying to an
incorrect previous domain. However, I later found out that pine can set
the reply address to whatever I want.
Thanks for your helpful replies
klee12
klee12
Simon wrote:
> > 2. I chose as my domain name .mit.edu. I chose it because I wanted
> > mail to go to alum.mit.edu. Might this domain name cause problems
now
> > with DHCP?
>
> It shouldn't normally, but there's no reason to set that as your
domain
> name just to send mail to a mail server under that domain.
Actually at first I set the domain to alum.mit.edu because I wanted
klee12
<<Check what range of addresses the router will assign. Or better
yet (IMHO), disable the DHCP server in the router and provide it
with appropriate routing table entries. It might be easy, for
example, to just give everything static addresses within the
range that the default routing table entries match. That way only
DHCP needs to be disabled, and it will still work if the defaults
pass out addresses 192.168.1.100 to 192.168.1.149. If I make the
assumption that, on boot up, the router will pass out the addresses in
order, then if I boot up my main computer first, it should get
192.168.1.100 and then the second on boot up should get 102.168.1.101.
If that conjecture works, and if I remember to boot up in the right
order, then I can pretend I have static IP addresses.
Thanks for your reply
klee12
Floyd L. Davidson
I wouldn't bet on *always* being able to do that.
Just disable the DHCP server, and use that range of addresses
for your static IP's. (Actually, it will work just fine if you
use those static IP addresses and don't disable DHCP too, as
long as nothing ever actually asks for an IP address from the
server.)
Simon
> Actually at first I set the domain to alum.mit.edu because I wanted
> replies to my email to go there ... too many people were replying to an
> incorrect previous domain. However, I later found out that pine can set
> the reply address to whatever I want.
That's settable in your MTA configuration too (sendmail, if you're
using the Slackware default).
> Thanks for your helpful replies
No problem.
marti
>
> Just disable the DHCP server, and use that range of addresses
> for your static IP's. (Actually, it will work just fine if you
> use those static IP addresses and don't disable DHCP too, as
> long as nothing ever actually asks for an IP address from the
> server.)
>
EXACTLY! Set your machines to use static addresses within the DHCP range and
leave DHCP turned on in the router and everything will work just like you
want it to.
There is no need to time the order of powering on your computers. If you get
a power outage it will be anarchy.
--
That's all folks
Floyd L. Davidson
>>
>> Just disable the DHCP server, and use that range of addresses
>> for your static IP's. (Actually, it will work just fine if you
>> use those static IP addresses and don't disable DHCP too, as
>> long as nothing ever actually asks for an IP address from the
>> server.)
>>
>
>EXACTLY! Set your machines to use static addresses within the DHCP range and
>leave DHCP turned on in the router and everything will work just like you
>want it to.
The DHCP server really should be turned off. As noted, leaving
it on only works as long as nothing ever actually asks for an IP
address... but if something does that could very definately
cause trouble.
Which is to say, it's okay if it's on during setup, but should
be disabled before the router is turned up for service.
>There is no need to time the order of powering on your computers. If you get
>a power outage it will be anarchy.
Yep. Plus each host on the network can actually know the IP
addresses of other hosts. (At least for a small network where
maintaining /etc/hosts on multiple hosts is not too much of a
burden.)