Re: DHCP & DNS

[Steve Blackwell]

---- Dave Burns <tburns(a)hawaii.edu&gt; wrote: 
>  My lazy ignorant suggestion is to reconfigure the router so that you
>  know the IP of the two boxes will not change and then use /etc/hosts. 
Yes, I know I could do that. It's OK when there are only 2 boxes but what if I had a
small office setup with, say, 100 PCs. It's not so practical then. I'm interested
in finding out if there is another way to make this work.

Steve

>  On 10/21/07, zephod(a)cfl.rr.com <zephod(a)cfl.rr.com&gt; wrote:
>  > I think my understanding is a little lacking on this subject (one of many).
>  >
>  > Here is my simple and, I suspect, very common setup: 2 PCs, one FC6 Linux, one
> Windows Vista and a Linksys wireless router. A DHCP server on the Linksys determines the
> IP addresses of the 2 machines.
>  >
>  > My question is: is it possible for either machine to ping the other without having
> to make an entry in its local hosts file?  Making entries in the hosts file doesn't
> seem like a good idea since the IP address could, in theory, change.
>  > The Linksys is a WRT54G and I don't think that it contains a DNS server. The
> names of my 2 machine should never get to a public DNS router since they are on a private
> network.
>  >
>  > Steve
>  >
>  > --
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>  > fedora-list(a)redhat.com
>  > To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>  >
>  
>  -- 
>  fedora-list mailing list
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DHCP & DNS

[Steve Searle]

Around 10:25pm on Sunday, October 21, 2007 (UK time), zephod(a)cfl.rr.com scrawled:

>  Yes, I know I could do that. It's OK when there are only 2 boxes
> but
>  what if I had a small office setup with, say, 100 PCs. It's not so
>  practical then. I'm interested in finding out if there is another way
>  to make this work. 
An office setup that you described would probably do this using a domain
name server (DNS) such as BIND.  This would serve public internet
addresses as well as the private network ones - the DHCP server can
update the DNS with the dynamic addresses when it allocates them.

You can set this up on your GNU/Linux box - I run one for my small home
network.  Note that if you do, your Windows box would need to be set to
point to the GNU/Linux one its primary DNS, but you would want a
secondrary DNS server for when the GNU/Linux one is down.

You can find some instructions I have written here:
http://www.stevesearle.com/tech/centos5.0.svr.html#bind

Steve

-- 

A:  Because it messes up the order in which people normally read text.
Q:  Why is top-posting a bad thing?

 22:30:49 up 22 days,  8:27,  2 users,  load average: 0.02, 0.05, 0.01

DHCP & DNS

[Dr J Austin]

On Sun, 2007-10-21 at 22:36 +0100, Steve Searle wrote:
>  Around 10:25pm on Sunday, October 21, 2007 (UK time),
> zephod(a)cfl.rr.com scrawled:
>  
>  > Yes, I know I could do that. It's OK when there are only 2 boxes but
>  > what if I had a small office setup with, say, 100 PCs. It's not so
>  > practical then. I'm interested in finding out if there is another way
>  > to make this work.
>  
>  An office setup that you described would probably do this using a domain
>  name server (DNS) such as BIND.  This would serve public internet
>  addresses as well as the private network ones - the DHCP server can
>  update the DNS with the dynamic addresses when it allocates them.
>  
>  You can set this up on your GNU/Linux box - I run one for my small home
>  network.  Note that if you do, your Windows box would need to be set to
>  point to the GNU/Linux one its primary DNS, but you would want a
>  secondrary DNS server for when the GNU/Linux one is down.
>  
>  You can find some instructions I have written here:
>  http://www.stevesearle.com/tech/centos5.0.svr.html#bind
>  
>  Steve
>  
>  -- 
>  fedora-list mailing list
>  fedora-list(a)redhat.com
>  To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list 
I found this useful when setting up my home DDNS

http://www.redhat.com/magazine/025nov06/features/dns/?sc_cid=bcm_edmsept_007
with a second chapter here

http://www.redhatmagazine.com/2006/12/15/dns/

I have a blog type file of how I set up my network
if anyone is interested.

John

[Fedora] Re: DHCP & DNS

[Ashley M. Kirchner]

zephod(a)cfl.rr.com wrote:
>  Yes, I know I could do that. It's OK when there are only 2 boxes
> but what if I had a small office setup with, say, 100 PCs. It's not so practical then.
> I'm interested in finding out if there is another way to make this work.
>     
    Rather than having the WRTG run the DHCP, let your FC machine do 
that.  Configure DHCP on FC to hand out the same IP for the WRTG, and 
set the rest of the pool as dynamic - this way the router will always 
have the same IP, which you can then use as the gateway for your 
network.  The other machines can have their IPs change if they so 
desire.  Then, on the same FC box, you also set up a local DNS server 
and let DHCP dynamically update it.  Set all the machines to use the FC 
as their DNS server and voila.  It no longer matters if the IPs change 
on the machines since the FC box will always have an updated list to 
hand out.

    As a practical example, I have this setup at the company where I 
work.  Our gateway also runs our DHCP server, and that same machine also 
runs a DNS server for the local network.  When DHCP hands out an IP for 
a machine on the local network, it also notifies the DNS server which in 
turn creates an ARPA entry in the 192.168.x.x range as well as insert an 
entry in the main domain name we use internally.  Now, any machine can 
simply type in the name of another machine to get to it (as opposed to 
having to figure out what their IP is each time.)

    In a way this would be overkill for simply two machines, which is 
what your initial request was for.  But if you plan on expanding, then 
it would make more sense to do DHCP with a dynamic DNS.

DHCP & DNS

[Dave Burns]

If you have 100 boxes, run DNS.  Sounds like you want (?) static host
names, might as well go for static IP too. Why not just make it all
static if they know each other and make assumptions about each other.

I just happen to know of an office with about 100 PCs in it, using NIS
and NFS means they need a static relationship between machine and IP.
(Well, again, it could be some other way but it is already complicated
enough.) They have some hosts set with static IP, others get IP from
DHCP but it is always the same (DHCP server config knows what IP
belongs to what MAC address), and a small number of laptops  share a
pool of IPs and do not have predictable IP.

Sounds to me like making everything totally dynamic is overkill in
your current situation, and would be skull-crackingly complicated with
100 PCs that think they know a lot about each other. Maybe there is
some applicable scale in between.

Or just don't assume that any relationship is static, then everything
can be dynamic.

What would really make you happy? Some sort of peer-to-peer DNS
without a server? Maybe you can use MAC addresses somehow?
Dave


On 10/21/07, zephod(a)cfl.rr.com <zephod(a)cfl.rr.com&gt; wrote:
>  ---- Dave Burns <tburns(a)hawaii.edu&gt; wrote:
>  > My lazy ignorant suggestion is to reconfigure the router so that you
>  > know the IP of the two boxes will not change and then use /etc/hosts.
>
>  Yes, I know I could do that. It's OK when there are only 2 boxes but what if I had a
> small office setup with, say, 100 PCs. It's not so practical then. I'm interested
> in finding out if there is another way to make this work.
>
>  Steve

DHCP & DNS

[Dr J Austin]

On Sun, 2007-10-21 at 12:16 -1000, Dave Burns wrote:
>  If you have 100 boxes, run DNS.  Sounds like you want (?) static
> host
>  names, might as well go for static IP too. Why not just make it all
>  static if they know each other and make assumptions about each other.
>  
>  I just happen to know of an office with about 100 PCs in it, using NIS
>  and NFS means they need a static relationship between machine and IP.
>  (Well, again, it could be some other way but it is already complicated
>  enough.) They have some hosts set with static IP, others get IP from
>  DHCP but it is always the same (DHCP server config knows what IP
>  belongs to what MAC address), and a small number of laptops  share a
>  pool of IPs and do not have predictable IP.
>  
>  Sounds to me like making everything totally dynamic is overkill in
>  your current situation, and would be skull-crackingly complicated with
>  100 PCs that think they know a lot about each other. Maybe there is
>  some applicable scale in between.
>  
>  Or just don't assume that any relationship is static, then everything
>  can be dynamic.
>  
>  What would really make you happy? Some sort of peer-to-peer DNS
>  without a server? Maybe you can use MAC addresses somehow?
>  Dave
>  
>  
>  On 10/21/07, zephod(a)cfl.rr.com <zephod(a)cfl.rr.com&gt; wrote:
>  >
>  > ---- Dave Burns <tburns(a)hawaii.edu&gt; wrote:
>  > > My lazy ignorant suggestion is to reconfigure the router so that you
>  > > know the IP of the two boxes will not change and then use /etc/hosts.
>  >
>  > Yes, I know I could do that. It's OK when there are only 2 boxes but what if I
> had a small office setup with, say, 100 PCs. It's not so practical then. I'm
> interested in finding out if there is another way to make this work.
>  >
>  > Steve
>   

Hi

I have found DDNS a great advantage as I am adding machines/virtual
machines/Fx Test releases quite frequently - it is a joy to use.

It is behind a routing firewall and is hopefully reasonably secure.

I attach my hints to myself below.
Please do not ask about the IP addresses used - its too long
a story!!!!!!!!!!

I also see that dnsmasq is suitable and is used by xen virtual machines?
man dnsmasq
"dnsmasq  is  a lightweight DNS, TFTP and DHCP server. It is intended to
provide coupled DNS and DHCP service to a LAN." .....


John

DHCP & DNS

[John Summerfield]

John Austin wrote:

>  I attach my hints to myself below.
>  Please do not ask about the IP addresses used - its too long
>  a story!!!!!!!!!! 
well, since those are public IP addresses, I'd just like to confirm that 
they're yours to use. If not, then you will have some difficulty 
accessing sites hosted on those IP addresses.






-- 

Cheers
John

-- spambait
1aaaaaaa(a)coco.merseine.nu  Z1aaaaaaa(a)coco.merseine.nu

Please do not reply off-list

DHCP & DNS

[Dr J Austin]

On Tue, 2007-10-23 at 18:34 +0800, John Summerfield wrote:
>  John Austin wrote:
>  
>  > I attach my hints to myself below.
>  > Please do not ask about the IP addresses used - its too long
>  > a story!!!!!!!!!!
>  
>  well, since those are public IP addresses, I'd just like to confirm that 
>  they're yours to use. If not, then you will have some difficulty 
>  accessing sites hosted on those IP addresses.
>  
>  
>  
>  
>  
>  
>  -- 
>  
>  Cheers
>  John
>  
>  -- spambait
>  1aaaaaaa(a)coco.merseine.nu  Z1aaaaaaa(a)coco.merseine.nu
>  
>  Please do not reply off-list
>   
My excuse is related to

http://web.jar.org.uk/pdf_dir/sem_2_documents_2003-4/sem_2_network_struct...

and laziness - but as long as they don't leak !!!!

John

DHCP & DNS

[Karl Larsen]

zephod(a)cfl.rr.com wrote:
>  ---- Dave Burns <tburns(a)hawaii.edu&gt; wrote: 
>    
> > My lazy ignorant suggestion is to reconfigure the router so that you
> > know the IP of the two boxes will not change and then use /etc/hosts.
> >     
>
>  Yes, I know I could do that. It's OK when there are only 2 boxes but what if I had a
> small office setup with, say, 100 PCs. It's not so practical then. I'm interested
> in finding out if there is another way to make this work.
>
>  Steve
>
>    
> > On 10/21/07, zephod(a)cfl.rr.com <zephod(a)cfl.rr.com&gt; wrote:
> >     
> >> I think my understanding is a little lacking on this subject (one of many).
> >>
> >> Here is my simple and, I suspect, very common setup: 2 PCs, one FC6 Linux, one
> Windows Vista and a Linksys wireless router. A DHCP server on the Linksys determines the
> IP addresses of the 2 machines.
> >>
> >> My question is: is it possible for either machine to ping the other without
> having to make an entry in its local hosts file?  Making entries in the hosts file
> doesn't seem like a good idea since the IP address could, in theory, change.
> >> The Linksys is a WRT54G and I don't think that it contains a DNS server. The
> names of my 2 machine should never get to a public DNS router since they are on a private
> network.
> >>
> >> Steve
> >>
> >> --
> >> fedora-list mailing list
> >> fedora-list(a)redhat.com
> >> To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
> >>
> >>       
> > -- 
> > fedora-list mailing list
> > fedora-list(a)redhat.com
> > To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
> >     
>
>     
    I was told by an expert to put my own ip and the ip of my DNS 
servers in /etc/hosts/ and it now looks like this:

[karl@k5di ~]$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1       localhost.localdomain   localhost
216.31.109.91   k5di.com
216.234.192.92  nameserver
216.234.213.130 nameserver

So you should do the same thing I think.



-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.

DHCP & DNS

[Frank Cox]

On Sun, 21 Oct 2007 16:48:42 -0600
Karl Larsen <k5di(a)zianet.com&gt; wrote:

>  216.31.109.91   k5di.com 
k5di.com doesn't belong to you.  In fact, it doesn't appear to belong to anyone
at this moment.

I'm not sure what kinds of problems can be caused by using a .com domain name
when it's not yours, but I don't think it can lead to anything good.

You would be well advised to either register k5di.com (which doesn't have to be
expensive) or use another domain name that you do own, or simply stick with
localhost.localdomain

-- 
MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com

DHCP & DNS

[Jacques B.]

On 10/21/07, Frank Cox <theatre(a)sasktel.net&gt; wrote:
>  On Sun, 21 Oct 2007 16:48:42 -0600
>  Karl Larsen <k5di(a)zianet.com&gt; wrote:
>
>  > 216.31.109.91   k5di.com
>
>  k5di.com doesn't belong to you.  In fact, it doesn't appear to belong to anyone
>  at this moment.
>
>  I'm not sure what kinds of problems can be caused by using a .com domain name
>  when it's not yours, but I don't think it can lead to anything good.
>
>  You would be well advised to either register k5di.com (which doesn't have to be
>  expensive) or use another domain name that you do own, or simply stick with
>  localhost.localdomain
>
>  --
>  MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com
>  
It doesn't cause any problems to use it in one's host file as long as
there isn't a site also by that domain name that you wish to visit.
I've created some false domain names for a classroom exercise and then
had the students populate their /etc/hosts file accordingly so that
when I had them navigate to the domain name in question they ended up
on a local server on our network.

In Karl's case when he puts that domain name in his address bar it
navigates to the IP he has there.  The only consequence would be if
that domain name was registered.  And then the impact would be to Karl
only.  He would not be able to navigate to it because your machine
uses /etc/hosts to resolve domain names first.  If not in there it
goes out to your DNS server.  So Karl's PC would resolve that domain
to the IP he has hence it would navigate to that IP, not to the IP for
the publicly registered domain by the same name.

I've modified my hosts file and put in the IP of my router and then
put in router for the domain name.  Now when I enter router in my
address bar I navigate to my router.  Likewise at work I did the same
for our email server.  I put in its IP and "mail" for the domain name.
 So I simply have to put mail in the address bar to navigate to my
webmail server.

Jacques B.

DHCP & DNS

[Frank Cox]

On Sun, 21 Oct 2007 19:49:54 -0400
"Jacques B." <jjrboucher(a)gmail.com&gt; wrote:

>  It doesn't cause any problems to use it in one's host file as
> long as
>  there isn't a site also by that domain name that you wish to visit. 
One problem that I can think of that this would cause outside of his own
private network would be with spam filtering.  k5di.com will likely appear
somewhere in his email headers (depending what client he is using) and when
that returns nxdomain his email could bounce or be scored up.  Moreso if
someone actually did register k5di.com for whatever reason, and set up a SPF
record for it.

On the other hand, that wouldn't inconvenience anyone other than Karl (and the
rest of us here who would have to listen to him moan about how nobody accepts
his email, of course.)

-- 
MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com

DHCP & DNS

[Karl Larsen]

Jacques B. wrote:
>  On 10/21/07, Frank Cox <theatre(a)sasktel.net&gt; wrote:
>    
> > On Sun, 21 Oct 2007 16:48:42 -0600
> > Karl Larsen <k5di(a)zianet.com&gt; wrote:
> >
> >     
> >> 216.31.109.91   k5di.com
> >>       
> > k5di.com doesn't belong to you.  In fact, it doesn't appear to belong to
> anyone
> > at this moment.
> >
> > I'm not sure what kinds of problems can be caused by using a .com domain name
> > when it's not yours, but I don't think it can lead to anything good.
> >
> > You would be well advised to either register k5di.com (which doesn't have to be
> > expensive) or use another domain name that you do own, or simply stick with
> > localhost.localdomain
> >
> > --
> > MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com
> >
> >     
>
>  It doesn't cause any problems to use it in one's host file as long as
>  there isn't a site also by that domain name that you wish to visit.
>  I've created some false domain names for a classroom exercise and then
>  had the students populate their /etc/hosts file accordingly so that
>  when I had them navigate to the domain name in question they ended up
>  on a local server on our network.
>
>  In Karl's case when he puts that domain name in his address bar it
>  navigates to the IP he has there.  The only consequence would be if
>  that domain name was registered.  And then the impact would be to Karl
>  only.  He would not be able to navigate to it because your machine
>  uses /etc/hosts to resolve domain names first.  If not in there it
>  goes out to your DNS server.  So Karl's PC would resolve that domain
>  to the IP he has hence it would navigate to that IP, not to the IP for
>  the publicly registered domain by the same name.
>
>  I've modified my hosts file and put in the IP of my router and then
>  put in router for the domain name.  Now when I enter router in my
>  address bar I navigate to my router.  Likewise at work I did the same
>  for our email server.  I put in its IP and "mail" for the domain name.
>   So I simply have to put mail in the address bar to navigate to my
>  webmail server.
>
>  Jacques B.
>
>     
    Thank you.

-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.

DHCP & DNS

[Jacques B.]

On 10/21/07, Karl Larsen <k5di(a)zianet.com&gt; wrote:
>  Jacques B. wrote:
>  > On 10/21/07, Frank Cox <theatre(a)sasktel.net&gt; wrote:
>  >
>  >> On Sun, 21 Oct 2007 16:48:42 -0600
>  >> Karl Larsen <k5di(a)zianet.com&gt; wrote:
>  >>
>  >>
>  >>> 216.31.109.91   k5di.com
>  >>>
>  >> k5di.com doesn't belong to you.  In fact, it doesn't appear to belong to
> anyone
>  >> at this moment.
>  >>
>  >> I'm not sure what kinds of problems can be caused by using a .com domain
> name
>  >> when it's not yours, but I don't think it can lead to anything good.
>  >>
>  >> You would be well advised to either register k5di.com (which doesn't have to
> be
>  >> expensive) or use another domain name that you do own, or simply stick with
>  >> localhost.localdomain
>  >>
>  >> --
>  >> MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com
>  >>
>  >>
>  >
>  > It doesn't cause any problems to use it in one's host file as long as
>  > there isn't a site also by that domain name that you wish to visit.
>  > I've created some false domain names for a classroom exercise and then
>  > had the students populate their /etc/hosts file accordingly so that
>  > when I had them navigate to the domain name in question they ended up
>  > on a local server on our network.
>  >
>  > In Karl's case when he puts that domain name in his address bar it
>  > navigates to the IP he has there.  The only consequence would be if
>  > that domain name was registered.  And then the impact would be to Karl
>  > only.  He would not be able to navigate to it because your machine
>  > uses /etc/hosts to resolve domain names first.  If not in there it
>  > goes out to your DNS server.  So Karl's PC would resolve that domain
>  > to the IP he has hence it would navigate to that IP, not to the IP for
>  > the publicly registered domain by the same name.
>  >
>  > I've modified my hosts file and put in the IP of my router and then
>  > put in router for the domain name.  Now when I enter router in my
>  > address bar I navigate to my router.  Likewise at work I did the same
>  > for our email server.  I put in its IP and "mail" for the domain name.
>  >  So I simply have to put mail in the address bar to navigate to my
>  > webmail server.
>  >
>  > Jacques B.
>  >
>  >
>      Thank you.
>
>  --
>
>          Karl F. Larsen, AKA K5DI
>          Linux User
>          #450462   http://counter.li.org.
>
>  --
>  fedora-list mailing list
>  fedora-list(a)redhat.com
>  To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>  
Welcome.  It's a convenient way to provide a website which does not
have a domain name with a domain name unique to your local machine as
you've done.  Or if instead of writing a very long domain name you can
do as you've done and resolve the IP for that domain name to something
shorter.  Of course using bookmarks can provide similar convenience.
But modifying one's host file can be convenient.  Try it for your
router/gateway.  Put its IP in your host file and then provide it
"router" as a domain name.  Then simply enter "router" in your
browser's address bar and voilà, you've navigated to your router
without the fuss of using its IP.

Sorry Steve, drifted a bit there.  Are you simply asking if the
machines can ping each other?  If that is your question, yes they can
in your scenario seeing they are getting an IP and subnet mask from
your DHCP server and hence on the same subnet.

Or are you asking if there is a way to have one machine be able to
ping the other without having to know its IP seeing it is dynamic?  My
suggestion there would be to have your DHCP server assign static IPs
(if it has that feature).  In absence of that feature manually
configure the static IP/subnet mask of the machines (ensuring it's the
same subnet as your router/gateway).

Also where you mention the host file, are you saying that both
machines are web servers with a domain name?

Jacques B.

DHCP & DNS

[Thufir]

On Sun, 21 Oct 2007 16:53:31 -0600, Frank Cox wrote:


>  You would be well advised to either register k5di.com (which
> doesn't
>  have to be expensive) or use another domain name that you do own, or
>  simply stick with localhost.localdomain 

A FQDN can always be registered at, for instance, <http://www.dyndns.com/
> ; whether or not a FQDN is required for the OP's purpose I
> couldn't  
say.  If one is required, there many free FQDN registration services.



-Thufir