How to configure DHCP Proxy?

A Former User

this is exactly the problem.
I got lost in all the options in the /etc/dnsmasq.d/ltsp.conf file.
what is the relevant options that I need to edit to make only the proxyDHCP to work?

Wayne Workman

As far as the options that you need, the ones listed in the WiKi page are pretty much all needed.

IF you look here:[url]http://fogproject.org/wiki/index.php/Using_FOG_with_an_unmodifiable_DHCP_server/_Using_FOG_with_no_DHCP_server#Setup_and_Configuration[/url]

You’ll see the upper section (for newer FOG versions):
[CODE]# Sample configuration for dnsmasq to function as a proxyDHCP server,

enabling LTSP clients to boot when an external, unmodifiable DHCP

server is present.

The main dnsmasq configuration is in /etc/dnsmasq.conf;

the contents of this script are added to the main configuration.

You may modify the file to suit your needs.

Don’t function as a DNS server:

port=0

Log lots of extra information about DHCP transactions.

log-dhcp

Dnsmasq can also function as a TFTP server. You may uninstall

tftpd-hpa if you like, and uncomment the next line:

enable-tftp

Set the root directory for files available via FTP.

tftp-root=/tftpboot

The boot filename.

dhcp-boot=pxelinux.0

rootpath option, for NFS

dhcp-option=17,/images

kill multicast

dhcp-option=vendor:PXEClient,6,2b

Disable re-use of the DHCP servername and filename fields as extra

option space. That’s to avoid confusing some old or broken DHCP clients.

dhcp-no-override

PXE menu. The first part is the text displayed to the user. The second is the timeout, in seconds.

pxe-prompt=“Press F8 for boot menu”, 3

The known types are x86PC, PC98, IA64_EFI, Alpha, Arc_x86,

Intel_Lean_Client, IA32_EFI, BC_EFI, Xscale_EFI and X86-64_EFI

This option is first and will be the default if there is no input from the user.

pxe-service=X86PC, “Boot from network”, pxelinux

A boot service type of 0 is special, and will abort the

net boot procedure and continue booting from local media.

pxe-service=X86PC, “Boot from local hard disk”, 0

If an integer boot service type, rather than a basename is given, then the

PXE client will search for a suitable boot service for that type on the

network. This search may be done by multicast or broadcast, or direct to a

server if its IP address is provided.

pxe-service=x86PC, “Install windows from RIS server”, 1

This range(s) is for the public interface, where dnsmasq functions

as a proxy DHCP server providing boot information but no IP leases.

Any ip in the subnet will do, so you may just put your server NIC ip here.

Since dnsmasq is not providing true DHCP services, you do not want it

handing out IP addresses. Just put your servers IP address for the interface

that is connected to the network on which the FOG clients exist.

If this setting is incorrect, the dnsmasq may not start, rendering

your proxyDHCP ineffective.

dhcp-range=192.168.1.10,proxy

This range(s) is for the private network on 2-NIC servers,

where dnsmasq functions as a normal DHCP server, providing IP leases.

dhcp-range=192.168.0.20,192.168.0.250,8h

For static client IPs, and only for the private subnets,

you may put entries like this:

dhcp-host=00:20:e0:3b:13:af,10.160.31.111,client111,infinite[/CODE]

the lines that have #'s are comments, and are not needed for a standard configuration…

If you take out ALL comments, you wind up with something like this:

[CODE]port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=pxelinux.0
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 3
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
cp-range=192.168.1.10,proxy[/CODE]

[FONT=Tahoma]And, all that stuff is pretty necessary… this stuff is the core of ProxyDHCP using dnsmasq.[/FONT]

[FONT=Tahoma]Go through what’s in the WiKi line by line.[/FONT]

[FONT=Tahoma]All the comments for the lines that are already enabled, those tell you exactly what those are…[/FONT]
Standard setups look just like this…

[FONT=Tahoma]You might check this post out for a working example, however this was wrote for someone else and you’ll have to change it as necessary: [url]http://fogproject.org/forum/threads/intel-undi-stuck-initializing.12729/#post-45331[/url][/FONT]

Jaymes Driver

[quote=“Amit Madmoni, post: 45437, member: 29386”]this is exactly the problem.
I got lost in all the options in the /etc/dnsmasq.d/ltsp.conf file.
what is the relevant options that I need to edit to make only the proxyDHCP to work?[/quote]

I understand that the config file can be a bit daunting, but we left the commented sections because they explain exactly how and why to use the option.

Wayne and uncle Frank are correct, we usually try to provide documentation on how to accomplish a task, we don’t edit files for you and hand them to you. I would be happy to help you to troubleshoot your issues, but I created and edited the articles on the wiki so that everyone could easily find the information and make use of it.

Wayne took this a step further, and I may edit the wiki article to include this, but you can remove the lines with a # in front of them, this is called a comment and DNSMASQ will gloss over the information without using it.

The portion below should help you to better understand where your information is required.
[code]
port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,x.x.x.x
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 3
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=10.0.0.10,proxy
[/code]

We need to edit the line “dhcp-boot=undionly.kpxe,x.x.x.x” and we need to replace the x.x.x.x with your FOG server ip address. according to your information the ip address is 172.16.0.200.

The correct line should read: dhcp-boot=undionly.kpxe,172.16.0.200

The next line to edit would be “dhcp-range=10.0.0.10,proxy” and we need to replace the 10.0.0.10 to an ip address you wish to use as a starting point for the proxy dhcp range.

Because this is only a Proxy and doesn’t actually have any bearing on your network, we recommend using the FOG server ip address as the starting dhcp address.

The correct line should read: dhcp-range=172.16.0.200,proxy

The only other line that should be edited in the ltsp.conf file would be the line “pxe-prompt=“Press F8 for boot menu”, 3”, You may change the number 3 to any number you would like. I usually set mine to 0, this is the screen that appears while DNSMASQ pulls up your boot information. Setting this number to 0 will allow for faster booting to the undionly.kpxe file.

So to wrap this all up you need to type the following command into a terminal

[code]
sudo gedit /etc/dnsmasq.d/ltsp.conf
[/code]

paste the following into the document and save

[code]
port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,172.16.0.200
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 0
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=172.16.0.200,proxy
[/code]

Now you need to symlink the undionly file so dnsmasq can boot, issue the following commands in the terminal
[code]
cd /tftpboot
sudo ln -s undionly.kpxe undionly.0
sudo service dnsmasq restart
[/code]

Now you should have a working DNSMASQ set up for your FOG Server.

Not to be mean, but please read the documentation, the wiki articles, and understand them.

We are more than willing to help you to understand what needs to be placed and where.

I do hope this helps clear up some confusion. I hope that my explanations and assistance outlined in this article helps to answer any future questions users may have.

I don’t feel like I helped you learn anything now that I have handed you the answers

When you restart dnsmasq, if you get an error reading “dnsmasq: failed to create listening socket for port 53: Address already in use failed!” You will likely need to perform the following actions since you are running Ubuntu 14.04:

[url]http://fogproject.org/wiki/index.php/Using_FOG_with_an_unmodifiable_DHCP_server/_Using_FOG_with_no_DHCP_server#Additional_Steps_for_12.04.4.2C_12.04.5.2C_14.04.2C_14.10[/url]

A Former User

First, thanks a lot for your answers guys.

Second, Jaymes Driver, this is exactly what I was looking for.
I don’t mean that i was looking for specific answer, but you answered all my questions. and don’t worry… i learned a lot!

Now my problem is when I’m restarting the dnsmasq service, I didn’t get this error: “dnsmasq: failed to create listening socket for port 53: Address already in use failed!”. instead I’m getting " Restarting DNS forwarder and DHCP server configuration syntax check"

again, thanks for everyone!

updae 1:
so I ran " dnsmasq -d", getting “dnsmasq: failed to create listening socket for port 53: Permission denied”
next - with sudo, getting:
[CODE]dnsmasq: started, version 2.68 cachesize 150
dnsmasq: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth
dnsmasq: reading /etc/resolv.conf
dnsmasq: using nameserver 209.222.18.218#53
dnsmasq: using nameserver 209.222.18.222#53
dnsmasq: using nameserver 10.0.0.1#53
dnsmasq: read /etc/hosts - 5 addresses[/CODE]

10.0.0.1 is my router-dhcp-dns
my real FOG real ip is 10.0.0.210

updae 2:
I’m trying to start dnsmasq service:
[CODE] * Starting DNS forwarder and DHCP server dnsmasq
dnsmasq: illegal repeated keyword at line 1 of /etc/dnsmasq.d/ltsp.conf
[fail]
[/CODE]

/etc/dnsmasq.d/ltsp.conf:
[CODE]port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,10.0.0.210
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 0
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=10.0.0.210,proxy
[/CODE]

update 3:
I figured it out.
There was a backup files in that directory. deleting them solved the problem.

A Former User

so I have another problem:
(Attached pic)

[url=“/_imported_xf_attachments/1/1872_boot error.PNG?:”]boot error.PNG[/url]

Wayne Workman

[quote=“Amit Madmoni, post: 45522, member: 29386”]so I have another problem:
(Attached pic)[/quote]

Have a look through here, pay attention to the permissions section: [url]http://fogproject.org/wiki/index.php/Troubleshoot_TFTP[/url]

Wayne Workman

Oh and also,

You need to make a copy (or symbolic link) of undionly.kpxe as undionly.0

This is a known issue with dnsmasq.

A Former User

failed at first stage.
I tried to telnet to port 69 on the server, but the port is closed.
In the server I checked that the tftpd-hpa service is running.

Wayne Workman

Try restarting the service,

and check your firewall.
[CODE]sudo iptables -L[/CODE]

A Former User

everything is good according to the “Troubleshoot TFTP” guide.
I also changed permissions.
yet, can’t boot from ws.
what should I do next?

Wayne Workman

What’s the output of this:

[CODE]ls -a /tftpboot[/CODE]

and, try changing /etc/dnsmasq.d/ltsp.conf:

this line:
[FONT=Consolas]dhcp-boot=undionly.kpxe,10.0.0.210 [/FONT]
[FONT=Consolas]to:[/FONT]
[FONT=Consolas]dhcp-boot=undionly.kpxe,[/FONT][FONT=Consolas]10.0.0.210[/FONT][FONT=Consolas],10.0.0.210[/FONT]

A Former User

output is attached.

I edited the /etc/dnsmasq.d/ltsp.conf file. same error.

[url=“/_imported_xf_attachments/1/1875_ls -a output.PNG?:”]ls -a output.PNG[/url]

Wayne Workman

What happens when you try to get undionly.kpxe through command line?

You can use Windows, or a Linux live disk for this. There are examples for testing in the “Troubleshoot TFTP” page.
Please post the output of it.

If you are successful, please do a TCP dump next, and post the resulting file. Here are some general instructions:

[CODE]sudo tcpdump -w issue.pcap -i eth0[/CODE]

You might need to change the interface name in the above command, seems like I have never had an interface named eth0 in Linux… This command will list all available interfaces. Pick the right one.
[CODE]ip link show[/CODE]

Run the above capture command on the FOG machine, then start the remote target host. Wait till it fails, then stop tcpdump (ctrl+c), transfer the PCAP file to your PC and examine it using wireshark. After the capture is completed, please use the MAC address of the target host as the filter for sender & receiver. This address will filter out ALL traffic that isn’t coming from or going to the target client.

Example Filter (change the MAC addresses):
[CODE]eth.dst == 00:0C:CC:76:4E:07 || eth.src==00:0C:CC:76:4E:07[/CODE]

Please also post this PCAP file so we can look at it and see what’s going on. And if you don’t filter the file for us, we will need the target host’s MAC as well so we can filter it.

A Former User

here is the pcap file:
[url]https://copy.com/iH3hRuI7Xcb6dfnY[/url]

I forgot to mention that the remote host is a vm, and the network interface configured as a bridge

Wayne Workman

The problem is that the client is asking for the wrong file.

It’s asking for pxelinux.0 which is not only wrong, but according to your screenshot that file does not exist - for real.

Re-examine ltsp.conf, make sure it’s giving either undionly.kpxe or undionly.0 and also restart the dnsmasq service and try again.

Wayne Workman

Also,

I’m not seeing a packet sent from 10.0.0.210 telling the client to use undionly.0, or 10.0.0.210 as the next-server…

If you look at the capture you posted, there are a total of TWO packets sent from the FOG server to the client.

This might mean that the DHCP server is already handing out the boot-server and file name, options 066 and 067.

Do you have a network hub? (not a switch)

A Former User

here is my ltsp.conf file:

[CODE]port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,10.0.0.210,10.0.0.210
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 0
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=10.0.0.210,proxy
[/CODE]

I dont have a network hub.
again, I’m running the client under virtual box. does it matter?

Tom Elliott

Change
[code]port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,10.0.0.210,10.0.0.210
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 0
pxe-service=X86PC, “Boot from network”, pxelinux
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=10.0.0.210,proxy[/code]

To:

[code]port=0
log-dhcp
tftp-root=/tftpboot
dhcp-boot=undionly.kpxe,10.0.0.210,10.0.0.210
dhcp-option=17,/images
dhcp-option=vendor:PXEClient,6,2b
dhcp-no-override
pxe-prompt=“Press F8 for boot menu”, 0
pxe-service=X86PC, “Boot from network”, undionly.kpxe
pxe-service=X86PC, “Boot from local hard disk”, 0
dhcp-range=10.0.0.210,proxy[/code]

Then make a copy of the undionly.kpxe to undionly.kpxe.0

[code]sudo cp /tftpboot/undionly.kpxe /tftpboot/undionly.kpxe.0[/code]

Jaymes Driver

[quote=“Amit Madmoni, post: 45626, member: 29386”]here is my ltsp.conf file: