Re: DHCP: how to manage dynamic address for the hosts in a network

[Tim]

On Thu, 2016-09-15 at 12:05 +0200, Peter Boy wrote:
> you can manually assign fix IP addresses to network devices. You
> router will find out by itself about IP addresses in use and won’t
> offer them in the DHCP process.

How?  And under what conditions?  If I remember correctly, a DHCP server
doesn't check that an IP address is in use, other than what it already
knows about through its own database (this "checking if it's free"
behaviour depends on how the DHCP server was programmed - whether it
does any checks, or just assumes that it's the god of IP address
assignments).  You'd have to rely on a client being given an address, it
trying it, and it refusing it if it (the client) finds an error (which
it may not do if the first client to have that IP doesn't respond, or
respond quick enough).

If by in-use, you mean currently in-use, then a DHCP server may or may
not know about some other device using that IP (and that may depend on
network topology), and may work around it.  For instance, if my DHCP
server tried to give out 192.168.1.20 to some second device when it's
already in use on my LAN (but that first device wasn't given that
address by the DHCP server), it'll try to give out that IP to the second
device, and it's only network errors that are going cause a problem.

But, an address that another computer, for example, uses when its turned
on, but is currently turned off, is not currently in-use, even if you
did want it reserved.

If you want things to have predictable IPs, you do need to fix them, not
rely on good luck.

If you're mixing static and dynamic IPs, you really need to pre-program
the DHCP server to handle that.  e.g. Tell the DHCP server that it can
freely assign IPs in a range (like 192.168.1.100 to 192.168.1.199) to
any random device, and you make sure that any static IPs that you set up
are outside of that range.  That applies whether you manually configure
individual devices to use static IPs, or centrally use a DHCP server to
give predetermined IPs to specific devices.

On my LAN, I have four ranges of IP addresses within one subnet that I
reserve for different purposes, and the DHCP server is configured
accordingly:

Static IPs configured in important devices (e.g. servers, routers), that
need to be self-configuring, independent of any DHCP server that may not
be available as they boot up.

e.g. x.y.z.1 to x.y.z.50

Fixed IPs that are always assigned to the same devices by the DHCP
server, for the usual client machines on the LAN.  I want these devices
to always have the same IP, for the sake of less headaches, but I want
to centrally manage them.  So the DHCP server is set to always give out
the same IPs to the devices recognised by their MACs (network hardware).

e.g. 192.168.1.51 to 192.168.1.100

Random dynamic IPs available to irregularly connected devices., for
visiting, drop-in test machines, unimportant devices, that I don't care
what their address is.  They're generally only clients, and nothing else
will need to connect *to* them.  This lets random things (internet
radios, games, whatever), simply work when plugged in.  This is the only
range that the DHCP is allowed to dole out randomly.

e.g. 192.168.1.101 to 192.168.1.200

Spare IPs, that I may use when dealing with debugging devices.  I can
freely set a device to use an IP in this range, knowing that there's not
going to be a bunfight with the DHCP server, and that nothing else
should be using them.

e.g. 192.168.1.201 to 192.168.1.253

They're all on the same subnet, and can all work with each other.  The
router (internet gateway) offers an isolated second subnet, so that
visitors could get onto the internet without any ability to mess with
the LAN (the router provides firewalling, as well as the network
addressing causing sub-net isolation).

e.g. 192.168.2.100 to 192.168.2.200

Networks can be as simple, or as complex as you need them to be.  But
messy "I don't know what I'm doing, and I'll randomly try things that
seem to work" just causes all sorts of headaches, sometimes immediately,
sometimes quite later.

-- 
tim@localhost ~]$ uname -rsvp

Linux 3.19.8-100.fc20.i686 #1 SMP Tue May 12 17:42:35 UTC 2015 i686

All mail to my mailbox is automatically deleted, there is no point trying
to privately email me, I will only read messages posted to the public lists.

George Orwell's '1984' was supposed to be a warning against tyranny, not
a set of instructions for supposedly democratic governments.
___
users mailing list -- users@lists.fedoraproject.org
To unsubscribe send an email to users-le...@lists.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Angelo Moreschini]

thank you

On Thu, Sep 15, 2016 at 4:39 PM, Ed Greshko  wrote:

>
>
> On 09/15/16 21:16, Angelo Moreschini wrote:
> > My router is D-Link DSL-6740U.
> >
> > The manual is to link :
> > ftp://ftp.dlink.ru/pub/VDSL2/DSL-6740U/Description/DSL-
> 6740U_B_T2A_User%20Manual_1.0.10_24.05.13_EN.pdf
> > .
>
> FWIW, you want pages 95 and 96.
>
> --
> You're Welcome Zachary Quinto
> --
> users mailing list
> users@lists.fedoraproject.org
> To unsubscribe or change subscription options:
> https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
> Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
> Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
> Have a question? Ask away: http://ask.fedoraproject.org
>
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Ed Greshko]

On 09/15/16 21:16, Angelo Moreschini wrote:
> My router is D-Link DSL-6740U.
>
> The manual is to link :
> ftp://ftp.dlink.ru/pub/VDSL2/DSL-6740U/Description/DSL-6740U_B_T2A_User%20Manual_1.0.10_24.05.13_EN.pdf
> .

FWIW, you want pages 95 and 96.

-- 
You're Welcome Zachary Quinto
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Angelo Moreschini]

thank you for your answers.

My router is D-Link DSL-6740U.

The manual is to link :
ftp://ftp.dlink.ru/pub/VDSL2/DSL-6740U/Description/DSL-6740U_B_T2A_User%20Manual_1.0.10_24.05.13_EN.pdf
.

I haven't so much experience with this kind of problem, and at the beginning
I thought that the only possibility was to setup of the router to fix the
assignment of the IP addresses..

But now I learned many things that I did not know from your answers .(mDNS
*,*  Zero-configuration networking, ..).

Now I have to study quite a lot.
I will ask again if I need.

Thank you

Angelo


On Thu, Sep 15, 2016 at 1:05 PM, Peter Boy 
wrote:

>
> > Am 15.09.2016 um 08:04 schrieb Angelo Moreschini <
> mrangelo.fed...@gmail.com>:
> >
> > My router assigns dynamically the IP addresses to the computers in the
> local network.
>
> If your router provides DHCP it usually provides a DNS service as well.
> You should log into your router and check the menus. Which router model are
> you using?
>
>
> > That is a problem to use applications that require IP addresses of the
> other computers in the network (i.e. managing network printers).
>
>
> Printers with an Ethernet connection usually by default observe for DHCP
> before assigning a random IP. So your printer should get its IP from your
> router as well. Your printer most likely tells the router’s DNS also its
> symbolic name, most likely some combination of manufacturer and model. The
> printers configuration page will tell you, or you can have a look into the
> device list of your
>  router which should show the IP address and the symbols name (smoother
> like e.g. „brother-mx“). So you might use that symbolic name in the printer
> configuration of your workstations.
>
> >
> > In other words, I would ask if, in linux environment, it is a
> possibility different to the setting up the router do assign static IP
> addresses, for managing this problem ( for example  using DNS...)??
>
> you can manually assign fix IP addresses to network devices. You router
> will find out by itself about IP addresses in use and won’t offer them in
> the DHCP process.
>
> Generally it’s a bad idea to mix devices with manually assigned IPs and
> devices using DHCP, at least if you have to manage more than 10 devices or
> so. After some time you forget some details and/or there is an update which
> changes some details, and you may run into issues. IT’s better to have a
> central management device, which is the router. Usually, you can configure
> the router to always assign the same IP address to a device depending on
> its MAC address.
>
>
>
>
>
>
> —
> Dr. Peter Boy
> Universität Bremen
> Mary-Sommerville-Str. 5
> 28359 Bremen
> Germany
>
> p...@zes.uni-bremen.de
> www.zes.uni-bremen.de
>
> 
>
> Are you looking for a web content management system for scientific
> research organizations?
> Have a look at http://www.scientificcms.org
> --
> users mailing list
> users@lists.fedoraproject.org
> To unsubscribe or change subscription options:
> https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
> Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
> Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
> Have a question? Ask away: http://ask.fedoraproject.org
>
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Peter Boy]

> Am 15.09.2016 um 08:04 schrieb Angelo Moreschini :
> 
> My router assigns dynamically the IP addresses to the computers in the local 
> network.

If your router provides DHCP it usually provides a DNS service as well. You 
should log into your router and check the menus. Which router model are you 
using?


> That is a problem to use applications that require IP addresses of the other 
> computers in the network (i.e. managing network printers).


Printers with an Ethernet connection usually by default observe for DHCP before 
assigning a random IP. So your printer should get its IP from your router as 
well. Your printer most likely tells the router’s DNS also its symbolic name, 
most likely some combination of manufacturer and model. The printers 
configuration page will tell you, or you can have a look into the device list 
of your
 router which should show the IP address and the symbols name (smoother like 
e.g. „brother-mx“). So you might use that symbolic name in the printer 
configuration of your workstations.

> 
> In other words, I would ask if, in linux environment, it is a  possibility 
> different to the setting up the router do assign static IP addresses, for 
> managing this problem ( for example  using DNS...)??

you can manually assign fix IP addresses to network devices. You router will 
find out by itself about IP addresses in use and won’t offer them in the DHCP 
process.

Generally it’s a bad idea to mix devices with manually assigned IPs and devices 
using DHCP, at least if you have to manage more than 10 devices or so. After 
some time you forget some details and/or there is an update which changes some 
details, and you may run into issues. IT’s better to have a central management 
device, which is the router. Usually, you can configure the router to always 
assign the same IP address to a device depending on its MAC address.






—
Dr. Peter Boy
Universität Bremen
Mary-Sommerville-Str. 5
28359 Bremen
Germany

p...@zes.uni-bremen.de
www.zes.uni-bremen.de



Are you looking for a web content management system for scientific research 
organizations?
Have a look at http://www.scientificcms.org
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Samuel Sieb]

On 09/14/2016 11:04 PM, Angelo Moreschini wrote:

My router assigns dynamically the IP addresses to the computers in the
local network.

That is a problem to use applications that require IP addresses of the
other computers in the network (i.e. managing network printers).

How to manage this problem (to use the IP addresses of computers in the
network) ?

_In other words,_ I would ask if, in linux environment, it is a
possibilitydifferent to the /setting up the router do assign static IP
addresses/,for managing this problem ( for example  using DNS...)??

Most network devices support the mdns (zeroconf, Bonjour, avahi) 
protocol.  If your Fedora system is setup correctly, which most likely 
means making sure that nss-mdns is installed, you should be able to use 
the mdns name wherever you need it.  If you know the name you setup for 
the printer, you should be able to ping it.  If you're not sure about 
the name, try running "avahi-browse -a" to see what's around.

--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Jon LaBadie]

On Thu, Sep 15, 2016 at 09:04:54AM +0300, Angelo Moreschini wrote:
> Hi,
> 
> I didn't get an answer to my preceding mail : "cups - the printer is not
> responding", so I try to get this answer with a different subject.

And you waited a whole day?  Or weren't the two responses what you wanted?

> 
> My router assigns dynamically the IP addresses to the computers in the
> local network.

So does mine.  But like most routers it can reserve specific addresses
for specific hosts.

I generally do that AND assign the same addresses as static IP addresses
to all my hosts.  The DHCP is just for unplanned connections.

> 
> That is a problem to use applications that require IP addresses of the
> other computers in the network (i.e. managing network printers).

Not if you use known, i.e. either dhcp reserved or static ip addresses.
You can then run a local DNS server (I use dnsmasq) or if your net is
small, distribute the addresses into the local /etc/hosts file on
each computer.

> 
> How to manage this problem (to use the IP addresses of computers in the
> network) ?
> 
> *In other words,* I would ask if, in linux environment, it is a
> possibility different
> to the *setting up the router do assign static IP addresses*, for managing
> this problem ( for example  using DNS...)??

see above.

JL
-- 
Jon H. LaBadie  jo...@jgcomp.com
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org

Re: DHCP: how to manage dynamic address for the hosts in a network

[Ed Greshko]

On 09/15/16 14:04, Angelo Moreschini wrote:
> Hi,
>
> I didn't get an answer to my preceding mail : "cups - the printer is not 
> responding",so
> I try to get this answer with a different subject.
>
> My router assigns dynamically the IP addresses to the computers in the local 
> network.
>
> That is a problem to use applications that require IP addresses of the other 
> computers
> in the network (i.e. managing network printers).
>
>
> How to manage this problem (to use the IP addresses of computers in the 
> network) ?
>
> _In other words,_ I would ask if, in linux environment, it is a  
> possibilitydifferent to
> the /setting up the router do assign static IP addresses/,for managing this 
> problem (
> for example  using DNS...)??
>

Several things to consider

First, most modern routers allow you to "fix" IP addresses to a given MAC 
address.  So,
when a device requests an IP address from the DHCP server it will supply the 
same IP
address for a given MAC address.  So, what router are you using?

Second, when it comes to printers many have network setups that allow you to 
assign a
static address. 

So, just because your router acts as a DHCP server doesn't mean you can't have 
static IP
addresses in your network. 





-- 
You're Welcome Zachary Quinto
--
users mailing list
users@lists.fedoraproject.org
To unsubscribe or change subscription options:
https://lists.fedoraproject.org/admin/lists/users@lists.fedoraproject.org
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org