DHCP-problem with internet

Chrizzieej · 07-15-2008, 09:42 AM

Hello,

I've got the following situation:
NIC0: is my internetconnection with a public IP-address, subnet, DNS-servers and a gateway from my provider.
NIC1: is my internal network and has IP-address 10.1.1.1.

I've got DHCP3-server installed with the following settings:

Code:

ddns-update-style none;

option domain-name "mydomain.nl";
option domain-name-servers pdns-provider sdns-provider;

default-lease-time 86400;
max-lease-time 604800;

authoritative;

subnet 10.1.1.0 netmask 255.255.255.0{
        range 10.1.1.100 10.1.1.110;
        option subnet-mask 255.255.255.0;
        option broadcast-address 10.1.1.255;
        option routers 10.1.1.1;

pdns-provider and sdns-provider are the DNS IP-adresses offcourse.

But the problem is, when my clients got an IP-address, they cannot connect to the internet. Clients get all the correct settings through DHCP but it doesn't work. IP-forwarding is enabled.

Am I missing something? Please help.

Greetz Chrizzieej

flitcraft33 · 07-15-2008, 11:01 AM

First, let me say I am an OpenBSD guy, not a linux guy so my suggestions may well be way off base. Having said that, can you ping the ISP's name server or boundary device by IP address? If so, and you are unable to connect by browser, it is possibly a DNS issue. I see that you have identified name servers by name. This may result in an inability to find the name server and therefore anything else. Add the IP address of a name server to your resolver file on a workstation

Chrizzieej · 07-15-2008, 06:18 PM

I cannot ping the ISP's nameservers or the IP-address from the first NIC!

exkor5000 · 07-15-2008, 07:51 PM

Hi

First of try:

Code:

tracert 64.233.169.104

and see where the packets stop.
if they don't go beyond your linux router then the problem is with forwarding.

What is your exact setup?
how do you get connected to the ISP in the first place?
If there is a cable/dsl modem why don't you configure DHCP right there?

Best

flitcraft33 · 07-16-2008, 09:45 AM

You say that your clients get an IP address, so the issue here appears to be routing more than dhcp. What is in the routing table on your dual homed server? In OpenBSD I use netstat -nr but your mileage may vary. You are looking for the default route, or route to 0.0.0.0 (which means basically anywhere not otherwise shown in the route table). You want this route to be out the proper interface, which I guess is NIC0 (the one leading to the ISP). My guess is that the routing table does not have it set this way so packets are not leaving your local network. If I am correct you will need to use the route command to add a new route to 0.0.0.0 indicating that you want to use NIC0. man route should give you guidance here. You may also need to use the route command to delete any existing, incorrect route to 0.0.0.0 .

Good luck.

Chrizzieej · 07-19-2008, 10:17 AM

I would explain the infrastructure to you guys:

eth0: ADSL-router (has 4 ports, with 4 public addresses, connected to port 1), this NIC has an static IP-adress (212.***.**.** with Subnet-mask 255.255.255.248), with the gateway and 2 DNS-servers of our ADSL-provider.
eth1: Has a static IP-address (10.1.1.1 with Subnet-mask 255.255.255.0) and is connected to a switch with all other clients.

My DHCP-server is configured as followed:

Code:

ddns-update-style none;

option domain-name "mydomain.nl";
option domain-name-servers pdns-provider sdns-provider;

default-lease-time 86400;
max-lease-time 604800;

authoritative;

subnet 10.1.1.0 netmask 255.255.255.0{
        range 10.1.1.100 10.1.1.110;
        option subnet-mask 255.255.255.0;
        option broadcast-address 10.1.1.255;
        option routers 10.1.1.1;

I want clients with IP-addresses 10.1.1.100 till 10.1.1.110 to use the internetconnection through eth0.

I hope you can help me now!