Name resolution for local names using DHCP

Unruh wrote:
> Charles Russell <NOSPAM@bellsouth.net> writes:

>>>>>> On Sun, 16 Dec 2007 14:20:28 -0600, Charles Russell wrote:
>>>>>>
>>>>>>> I can't figure out how to get name resolution for computers on my
>>>>>>> home WLAN, though everything works all right if I type in explicit IP
>>>>>>> addresses. The IP addresses will vary because of DHCP, so I can't
>>>>>>> simply put them in /etc/hosts.
>>>>>>>
>>>>>>> The hostnames and IP addresses are all known to the router (Linksys
>>>>>>> wrt54g), as I can confirm by querying the router. Should the router
>>>>>>> not resolve these local hostnames? Or do I misunderstand how this
>>>>>>> should work under DHCP?

> This would by far be the easiest thing to do, just assign ip addresses to
> mac addresses and be done with it.

OK, you folks have convinced me. Thanks.

Unruh wrote:
> Charles Russell <NOSPAM@bellsouth.net> writes:
>
>> Unruh wrote:
>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>
>>>> Charles Russell wrote:
>>>>> I can't figure out how to get name resolution for computers on my home
>>>>> WLAN, though everything works all right if I type in explicit IP
>>>>> addresses. The IP addresses will vary because of DHCP, so I can't
>>>>> simply put them in /etc/hosts.
>>>>>
>>>>> The hostnames and IP addresses are all known to the router (Linksys
>>>>> wrt54g), as I can confirm by querying the router. Should the router not
>>>>> resolve these local hostnames? Or do I misunderstand how this should
>>>>> work under DHCP?
>>>> Thanks for the responses, everybody. I infer that there is no simple
>>>> fix within the capability of the DHCP server in my $50 Linksys wrt54g
>>>> router. Given that there is no simple fix, and that the only problem is
>>>> that I have to manually enter IP addresses whenever I do local ftp or
>>>> ssh, I think I'll follow the principle: "If it ain't broke (much), don't
>>>> fix it (much)."
>>> Some routers allow you to tell the dhcp service on the router to allways
>>> assign ip address X to MAC address Y. Look through the manual to see if
>>> your router allows that.
>>>
>>>
>> Yes, it does. But why should static IP addresses be required, when the
>> DHCP server already has the hostname-IP address associations it needs to
>> resolve the local hostname?
>
> You have become fixated on your particular solution to the problem. Let go.
> Or spend you life trying to persuade Linksys to do it your way.
>

Just trying to understand a bit more about networking, and to find the
simplest solution to a noncritical problem.

OK, static addresses.

Thanks.

Charles Russell wrote:
> Unruh wrote:
>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>
>>> Unruh wrote:
>>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>>
>>>>> Charles Russell wrote:
>>>>>> I can't figure out how to get name resolution for computers on my
>>>>>> home WLAN, though everything works all right if I type in explicit
>>>>>> IP addresses. The IP addresses will vary because of DHCP, so I
>>>>>> can't simply put them in /etc/hosts.
>>>>>>
>>>>>> The hostnames and IP addresses are all known to the router
>>>>>> (Linksys wrt54g), as I can confirm by querying the router. Should
>>>>>> the router not resolve these local hostnames? Or do I
>>>>>> misunderstand how this should work under DHCP?
>>>>> Thanks for the responses, everybody. I infer that there is no
>>>>> simple fix within the capability of the DHCP server in my $50
>>>>> Linksys wrt54g router. Given that there is no simple fix, and that
>>>>> the only problem is that I have to manually enter IP addresses
>>>>> whenever I do local ftp or ssh, I think I'll follow the principle:
>>>>> "If it ain't broke (much), don't fix it (much)."
>>>> Some routers allow you to tell the dhcp service on the router to
>>>> allways
>>>> assign ip address X to MAC address Y. Look through the manual to see if
>>>> your router allows that.
>>>>
>>>>
>>> Yes, it does. But why should static IP addresses be required, when
>>> the DHCP server already has the hostname-IP address associations it
>>> needs to resolve the local hostname?
>>
>> You have become fixated on your particular solution to the problem.
>> Let go.
>> Or spend you life trying to persuade Linksys to do it your way.
>>
>
> Just trying to understand a bit more about networking, and to find the
> simplest solution to a noncritical problem.
>
> OK, static addresses.
>
> Thanks.
I know I'm jumping in late, but static addresses are not a terribly good
idea - they don't scale in the sense that if you add another computer to
a network of n machines, then you have to change the /etc/hosts file of
all n existing machines.

1. Are you sure that your router can't to hostname to IP address
translations? It may just be that it has a wrong idea of your domain
names. If the host name of another computer is, say, machine, try to
resolve (e.g. with the command hosts):

machine.

(the following dot will stop your own computer appending its own idea of
the domain name)

Otherwise, look at the router's idea of the domain name and try to resolve:

machine.domain.name.

(if the domain name is domain.name)

Of course that may not work either, but it will test whether your router
can resolve local hostnames.

2. Run avahi. Then each machine will advertise its own hostname and IP
address and you will be able to resolve say, machine, as machine.local

Robert

Charles Russell <NOSPAM@bellsouth.net> wrote:
> Unruh wrote:
>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>
>>> Charles Russell wrote:
>>>> I can't figure out how to get name resolution for computers on my home
>>>> WLAN, though everything works all right if I type in explicit IP
>>>> addresses. The IP addresses will vary because of DHCP, so I can't
>>>> simply put them in /etc/hosts.
>>>>
>>>> The hostnames and IP addresses are all known to the router (Linksys
>>>> wrt54g), as I can confirm by querying the router. Should the router not
>>>> resolve these local hostnames? Or do I misunderstand how this should
>>>> work under DHCP?
>>
>>> Thanks for the responses, everybody. I infer that there is no simple
>>> fix within the capability of the DHCP server in my $50 Linksys wrt54g
>>> router. Given that there is no simple fix, and that the only problem is
>>> that I have to manually enter IP addresses whenever I do local ftp or
>>> ssh, I think I'll follow the principle: "If it ain't broke (much), don't
>>> fix it (much)."
>>
>> Some routers allow you to tell the dhcp service on the router to allways
>> assign ip address X to MAC address Y. Look through the manual to see if
>> your router allows that.
>>
>>
> Yes, it does. But why should static IP addresses be required, when the
> DHCP server already has the hostname-IP address associations it needs to
> resolve the local hostname?

Because that's not the function of the DHCP server, it's the DNS
server's function. DHCP is designed to get you an ip address and some
other optional information useful in connecting to a network. Name
resolution is an entirely different thing.

Jerry

Robert Harris wrote:
> Charles Russell wrote:
>> Unruh wrote:
>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>
>>>> Unruh wrote:
>>>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>>>
>>>>>> Charles Russell wrote:
>>>>>>> I can't figure out how to get name resolution for computers on my
>>>>>>> home WLAN, though everything works all right if I type in explicit
>>>>>>> IP addresses. The IP addresses will vary because of DHCP, so I
>>>>>>> can't simply put them in /etc/hosts.
>>>>>>>
>>>>>>> The hostnames and IP addresses are all known to the router
>>>>>>> (Linksys wrt54g), as I can confirm by querying the router. Should
>>>>>>> the router not resolve these local hostnames? Or do I
>>>>>>> misunderstand how this should work under DHCP?
>>>>>> Thanks for the responses, everybody. I infer that there is no
>>>>>> simple fix within the capability of the DHCP server in my $50
>>>>>> Linksys wrt54g router. Given that there is no simple fix, and that
>>>>>> the only problem is that I have to manually enter IP addresses
>>>>>> whenever I do local ftp or ssh, I think I'll follow the principle:
>>>>>> "If it ain't broke (much), don't fix it (much)."
>>>>> Some routers allow you to tell the dhcp service on the router to
>>>>> allways
>>>>> assign ip address X to MAC address Y. Look through the manual to see if
>>>>> your router allows that.
>>>>>
>>>>>
>>>> Yes, it does. But why should static IP addresses be required, when
>>>> the DHCP server already has the hostname-IP address associations it
>>>> needs to resolve the local hostname?
>>> You have become fixated on your particular solution to the problem.
>>> Let go.
>>> Or spend you life trying to persuade Linksys to do it your way.
>>>
>> Just trying to understand a bit more about networking, and to find the
>> simplest solution to a noncritical problem.
>>
>> OK, static addresses.
>>
>> Thanks.
> I know I'm jumping in late, but static addresses are not a terribly good
> idea - they don't scale in the sense that if you add another computer to
> a network of n machines, then you have to change the /etc/hosts file of
> all n existing machines.
>
> 1. Are you sure that your router can't to hostname to IP address
> translations? It may just be that it has a wrong idea of your domain
> names. If the host name of another computer is, say, machine, try to
> resolve (e.g. with the command hosts):
>
> machine.
>
> (the following dot will stop your own computer appending its own idea of
> the domain name)
>
> Otherwise, look at the router's idea of the domain name and try to resolve:
>
> machine.domain.name.
>
> (if the domain name is domain.name)
>
> Of course that may not work either, but it will test whether your router
> can resolve local hostnames.
>
> 2. Run avahi. Then each machine will advertise its own hostname and IP
> address and you will be able to resolve say, machine, as machine.local
>
> Robert

Thanks. I haven't time at the moment to experiment, but in the meanwhile
I have a question about the domain name. My network was originally set
up as a Windows XP network, with workgroup name "MSHOME", and later I
added a Linux box and a MacOSX box, both of which got handled
automatically by DHCP with no further router configuration. (Everything
works except for local name resolution, and even that works with samba
clients. MaxOSX and Linux behave identically.) As far as I know, I don't
have a named "domain", unless that is the same as the Windows network
workgroup.

With Linux, dhcpcd (I think) puts the line "search Belkin" into
resolv.conf. I have no idea what that is for.

Charles Russell wrote:
> Robert Harris wrote:
>> Charles Russell wrote:

>>> [snip]
>> I know I'm jumping in late, but static addresses are not a terribly good
>> idea - they don't scale in the sense that if you add another computer to
>> a network of n machines, then you have to change the /etc/hosts file of
>> all n existing machines.
>>
>> 1. Are you sure that your router can't to hostname to IP address
>> translations? It may just be that it has a wrong idea of your domain
>> names. If the host name of another computer is, say, machine, try to
>> resolve (e.g. with the command hosts):
>>
>> machine.
>>
>> (the following dot will stop your own computer appending its own idea of
>> the domain name)
>>
>> Otherwise, look at the router's idea of the domain name and try to
>> resolve:
>>
>> machine.domain.name.
>>
>> (if the domain name is domain.name)
>>
>> Of course that may not work either, but it will test whether your router
>> can resolve local hostnames.
>>
>> 2. Run avahi. Then each machine will advertise its own hostname and IP
>> address and you will be able to resolve say, machine, as machine.local
>>
>> Robert
>
> Thanks. I haven't time at the moment to experiment, but in the meanwhile
> I have a question about the domain name. My network was originally set
> up as a Windows XP network, with workgroup name "MSHOME", and later I
> added a Linux box and a MacOSX box, both of which got handled
> automatically by DHCP with no further router configuration. (Everything
> works except for local name resolution, and even that works with samba
> clients. MaxOSX and Linux behave identically.) As far as I know, I don't
> have a named "domain", unless that is the same as the Windows network
> workgroup.
>
> With Linux, dhcpcd (I think) puts the line "search Belkin" into
> resolv.conf. I have no idea what that is for.

That means that your Linux machine will search for machine.Belkin when
you ask it to search for machine (the resolv.conf man page tells a
fuller story). The name "Belkin" probably comes from your router; there
will be a file somewhere which on my (Debian) system is
/var/log/dhcp3/dhclient.eth0.leases which lists the parameters that your
router has sent.

Tell your router that your domain name is "local" (without the quotes)
and, after you have had a dhcp response from your router, make sure that
your /etc/resolv.conf contains the line: "search local".

Domain is nothing to so with workgroup name; it is generally like
"bellsouth.net" (if the fully qualified name of your computer is
"mycomputer.bellsouth.net).

Robert

On Mon, 17 Dec 2007 15:40:33 -0600, Charles Russell wrote:

>
> Thanks. I haven't time at the moment to experiment, but in the meanwhile
> I have a question about the domain name. My network was originally set
> up as a Windows XP network, with workgroup name "MSHOME", and later I
> added a Linux box and a MacOSX box, both of which got handled
> automatically by DHCP with no further router configuration. (Everything
> works except for local name resolution, and even that works with samba
> clients. MaxOSX and Linux behave identically.) As far as I know, I don't
> have a named "domain", unless that is the same as the Windows network
> workgroup.

domain name and workgroup are not the same. On my LAN the domain name
is not a registered domain so I put .invalid on the end of it. See

$ hostname --domain
home.invalid

looking in /etc/samba/smb.conf we see the work group defined

[global]
# 1. Server Naming Options:
# workgroup = NT-Domain-Name or Workgroup-Name
workgroup = MDKGROUP



> With Linux, dhcpcd (I think) puts the line "search Belkin" into
> resolv.conf. I have no idea what that is for.

Yep, search line is handed out by your dhcp server and placed there by
your dhcp client.

I remove the search line to speed up some dns look ups when I use dhcp
I use static ip for all machines on my LAN just to keep things simple.

That allows dns to use dns nameservers without searching the domain first.

Robert Harris <robert.f.harris@blueyonder.co.uk> writes:

>Charles Russell wrote:
>> Unruh wrote:
>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>
>>>> Unruh wrote:
>>>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>>>
>>>>>> Charles Russell wrote:
>>>>>>> I can't figure out how to get name resolution for computers on my
>>>>>>> home WLAN, though everything works all right if I type in explicit
>>>>>>> IP addresses. The IP addresses will vary because of DHCP, so I
>>>>>>> can't simply put them in /etc/hosts.
>>>>>>>
>>>>>>> The hostnames and IP addresses are all known to the router
>>>>>>> (Linksys wrt54g), as I can confirm by querying the router. Should
>>>>>>> the router not resolve these local hostnames? Or do I
>>>>>>> misunderstand how this should work under DHCP?
>>>>>> Thanks for the responses, everybody. I infer that there is no
>>>>>> simple fix within the capability of the DHCP server in my $50
>>>>>> Linksys wrt54g router. Given that there is no simple fix, and that
>>>>>> the only problem is that I have to manually enter IP addresses
>>>>>> whenever I do local ftp or ssh, I think I'll follow the principle:
>>>>>> "If it ain't broke (much), don't fix it (much)."
>>>>> Some routers allow you to tell the dhcp service on the router to
>>>>> allways
>>>>> assign ip address X to MAC address Y. Look through the manual to see if
>>>>> your router allows that.
>>>>>
>>>>>
>>>> Yes, it does. But why should static IP addresses be required, when
>>>> the DHCP server already has the hostname-IP address associations it
>>>> needs to resolve the local hostname?
>>>
>>> You have become fixated on your particular solution to the problem.
>>> Let go.
>>> Or spend you life trying to persuade Linksys to do it your way.
>>>
>>
>> Just trying to understand a bit more about networking, and to find the
>> simplest solution to a noncritical problem.
>>
>> OK, static addresses.
>>
>> Thanks.
>I know I'm jumping in late, but static addresses are not a terribly good
>idea - they don't scale in the sense that if you add another computer to
>a network of n machines, then you have to change the /etc/hosts file of
>all n existing machines.

It depends on what the value of n is. If it is 3 then that is not a problem
If it is 10 or 1000 then it is. Most homes have at most 3 computers.
YOu can also write a script to transfer the /etc/hosts file to all machines
when needed.
Also you could set up one of the machines as a dns server and use it to
resolve for the others. This is much more work than updating /etc/hosts
once a year for 3 machines. If you have 10 or 100 or more, then it may well
be the way to go.


>1. Are you sure that your router can't to hostname to IP address
>translations? It may just be that it has a wrong idea of your domain
>names. If the host name of another computer is, say, machine, try to
>resolve (e.g. with the command hosts):

The amount of time he has already spent just typing his queries exceeds the
work of updating /etc/hosts for the next 5 years.



>machine.

>(the following dot will stop your own computer appending its own idea of
>the domain name)

>Otherwise, look at the router's idea of the domain name and try to resolve:

>machine.domain.name.

>(if the domain name is domain.name)

>Of course that may not work either, but it will test whether your router
>can resolve local hostnames.

>2. Run avahi. Then each machine will advertise its own hostname and IP
>address and you will be able to resolve say, machine, as machine.local

>Robert

Robert Harris wrote:
> Charles Russell wrote:
>> Unruh wrote:
>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>
>>>> Unruh wrote:
>>>>> Charles Russell <NOSPAM@bellsouth.net> writes:
>>>>>
>>>>>> Charles Russell wrote:
>>>>>>> I can't figure out how to get name resolution for computers on my
>>>>>>> home WLAN, though everything works all right if I type in explicit
>>>>>>> IP addresses. The IP addresses will vary because of DHCP, so I
>>>>>>> can't simply put them in /etc/hosts.


>
> 1. Are you sure that your router can't to hostname to IP address
> translations? It may just be that it has a wrong idea of your domain
> names. If the host name of another computer is, say, machine, try to
> resolve (e.g. with the command hosts):
>
> machine.
>
> (the following dot will stop your own computer appending its own idea of
> the domain name)

You mean ping dell03. or nslookup dell03. ? No luck.
>
> Otherwise, look at the router's idea of the domain name

In the router setup page, domain name is empty.

and try to resolve:
>
> machine.domain.name.
>
> (if the domain name is domain.name)
>
> Of course that may not work either, but it will test whether your router
> can resolve local hostnames.
>
> 2. Run avahi. Then each machine will advertise its own hostname and IP
> address and you will be able to resolve say, machine, as machine.local

Not in my linux distribution. Not likely in OSX, but haven't looked.
Would it give any information I can't get directly from the router,
which can display the hostnames and IP addresses assigned by DHCP?
>
> Robert

Unruh wrote:

> The amount of time he has already spent just typing his queries exceeds the
> work of updating /etc/hosts for the next 5 years.

Yes. Or to create aliases for the IP addresses as they change from time
to time. But maybe I have learned something along the way.