Re: dhcp server and isp's dns...

From: Luke (clairst_at_uiuc.edu)
Date: 12/30/03 

Date: Tue, 30 Dec 2003 04:17:19 GMT

On 2003-12-30, Andrey Asadchev <dont.spam.me@softhome.net> wrote:
> Luke wrote:
>> How can I pass the DNS info along to my clients when the DNS info is
>> dynamically assigned? I see in the DHCP howto that you can do it easily
>> if they are static, but what about dynamic?
>
> I doubt the DNS servers of your provider will be changing IPs often
> enough to cause your discomfort. They are dynamically assigned, yes -
> but they are the same every time (unless the provider is doing something
> really really weird). Get the nameservers IPs from /etc/resolv.conf on
> the router and put them into /etc/dhcp(3)?/dhcpd.conf.

How do my hardware routers handle this? Seems like it should be
possible with dhcpd, and its definitely the preferred behavior for me in
this case (though I do recognize that the DNS servers will change
infrequently).

>
> Alternatively you can setup your own DNS server. apt-get install bind9
> will install DNS server. You dont really have to do anything besides
> telling your client machines to use your internal DNS server. I.e: your
> DNS server IP is 192.168.1.10. In dhcpd.conf put
> "domain-name-servers 192.168.1.10;"
>

I may get around to this eventually, but ideally, i'd like to have as
few services as possible running on this new machine... so I'd like to
say no to this unless necessary...

>
>> And what's the best way to add the
>> /sbin/route add -host 255.255.255.255 dev eth1
>
> Why do you want to do that? Win98 and above work fine without it. Cant
> say much about win95 since never had them on network.
> In any case, edit your /etc/network/interfaces to read someting like
>
Quoted from DHCPd README:

In order for dhcpd to work correctly with picky DHCP clients (e.g.,
Windows 95), it must be able to send packets with an IP destination
address of 255.255.255.255. Unfortunately, Linux insists on changing
255.255.255.255 into the local subnet broadcast address (in this case,
the address would be 192.5.5.223). This results in a DHCP protocol
violation. While many DHCP clients don't notice the problem, some (e.g.,
all Microsoft DHCP clients) will recognize the violation. Clients that
have this problem will appear not to see DHCPOFFER messages from the
server.

</QUOTE>

So what I thought this meant was that "all Mircosoft DHCP clients" would
need this workaround, as mentioned above... sounds like from your post,
that this is not the case, however. I don't need to support win95, so I
guess I won't bother with it then.

><snip>
> iface eth0 inet static
> address 192.168.1.1
> netmask 255.255.255.0
> up /sbin/route add -host 255.255.255.255 dev eth1
></snip>
>
>
> Not a valid concern. How often is your dhcp updated anyways? Mine has
> been updated only once since woody came out.

Huh, I would've thought the /etc/init.d/dhcp scripts would have been
replaced each upgrade... thanks for the info 

-- 
Luke StClair
run_faster@hotmail.com
PGP key: http://www.students.uiuc.edu/~clairst

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