Topic: Relay DNS server on DHCP

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Post #1

jlazkano

19 Nov 2009, 17:38

Hello, I have a Fonera with Openwrt, I want to relay the DNS servers to the computers with DHCP, I want to ask to DNS server directly from my computer.

This is my Openwrt network configuration:

# cat /etc/config/network 

config 'interface' 'loopback'
    option 'ifname' 'lo'
    option 'proto' 'static'
    option 'ipaddr' '127.0.0.1'
    option 'netmask' '255.0.0.0'

config 'interface' 'lan'
    option 'type' 'bridge'
    option 'proto' 'static'
    option 'netmask' '255.255.255.0'
    option 'ifname' 'eth0.0'
    option 'ipaddr' '192.168.2.1'
    option 'gateway' '192.168.1.1'
    option 'dns' '87.216.1.65 87.216.1.66'

config 'interface' 'wan'
    option 'ifname' 'eth0.1'
    option 'proto' 'static'
    option 'ipaddr' '192.168.1.2'
    option 'netmask' '255.255.255.0'
    option 'gateway' '192.168.1.1'
    option 'dns' '87.216.1.65 87.216.1.66'

And this is what I get on my Gnome laptop from DHCP:

How can I solve it? Is it better to manage the DNS asks from Openwrt?

Thanks for all and best regards.

Post #2

alaric

19 Nov 2009, 18:05

Firstly your network configuration has nothing to do with DNS or DHCP *serving*.

To do dhcp options, you need to make your changes in the /etc/config/dhcp file. See the output from `dnsmasq --help dhcp` to get the translation from option name to option number.

6 is the dns server option. Here is the format of the entry for the config file:

list 'dhcp_option' '6,192.168.1.200'

So to fix your's:

config 'dhcp' 'lan'
        option 'interface' 'lan'
        option 'start' '100'
        option 'limit' '150'
        option 'leasetime' '12h'
        list 'dhcp_option' '6,87.216.1.65 87.216.1.66'

Apart from the list option, all the rest are the basic defaults, so simply add that one line to your current lan config section in /etc/config/dhcp

Post #3

jlazkano

19 Nov 2009, 18:41

Thanks for your reply, I just probe to add this line but now I can get anything from DHCP, I must configure an static IP on the laptop to enter to the router.

There isn't an other "cleaner" way to do that? It will be great to take the DNS servers from my /etc/config/network configuration automatically.

Thanks for all, I will continue searching.

Post #4

alaric

19 Nov 2009, 19:02

OK, my bad... there's a comma missing:

list 'dhcp_option' '6,87.216.1.65,87.216.1.66'

As for an easier way there is a web interface called LuCI that will allow you to enter DHCP options, however you still need to use other resources to find the right option and formatting.

Post #5

jlazkano

19 Nov 2009, 19:13

Ohhh!!! Thanks! Now it works.

I will search for more, I need to take the DNS server from my ISP router that is connected on WAN interface, I will look for this.

Thanks again and best regards!

Post #6

alaric

19 Nov 2009, 19:35

Why wouldn't you want the Fonera to service DNS requests? That really doesn't make much sense.

The discussion might have continued from here.

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