Jeff swicegood
asked on
DHCP clients get wrong DNS after setting up separate PXE boot server
My Setup:
Router: Routerboard 1100hx2
RouterOS:version 6
TFTP boot server running in Ubuntu 12.04
I am trying to run FOG imaging solution .32. Everything works fine and I can PXE boot PC's and image PC's but sometimes other PC's on the network pull the wrong DNS, thus disconnecting them from Internet. I guess this comes from running two DHCP servers on the same network. In my previous router DD-WRT this was fixed by adding DNSMasq options. This router is completely different.
I have tried setting the DHCP Server>nextserver to the address of my TFTP server (192.168.0.45). and the serverbootfile to pxelinux.0. I have not added any other settings. Also I have tried setting whatever DNS settings I could find in the configs of 192.168.0.45.
Router: Routerboard 1100hx2
RouterOS:version 6
TFTP boot server running in Ubuntu 12.04
I am trying to run FOG imaging solution .32. Everything works fine and I can PXE boot PC's and image PC's but sometimes other PC's on the network pull the wrong DNS, thus disconnecting them from Internet. I guess this comes from running two DHCP servers on the same network. In my previous router DD-WRT this was fixed by adding DNSMasq options. This router is completely different.
I have tried setting the DHCP Server>nextserver to the address of my TFTP server (192.168.0.45). and the serverbootfile to pxelinux.0. I have not added any other settings. Also I have tried setting whatever DNS settings I could find in the configs of 192.168.0.45.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
hi,
you can enter this line to dhcp.conf file and run your fog by client system.
if substring (option vendor-class-identifier, 0, 9) = "PXEClient" {
next-server Fog Server ip;
filename "pxelinux.0";
}
you can enter this line to dhcp.conf file and run your fog by client system.
if substring (option vendor-class-identifier, 0, 9) = "PXEClient" {
next-server Fog Server ip;
filename "pxelinux.0";
}
what rajeev2353 suggested will make ALL your PXE client booting with pxelinux.0 from "Fog Server IP".
But this will NOT have an impact on the DNS settings that DHCP server sends.
In my opinion, you should remove all DNS settings from the PXE server and keep only the DNS settings that the DHCP Server sends to clients.
Also, the PXE server should not send IP config (including DNS, gateway) etc., just the Network Boot Program name and location (tftp server), along with specific PXE/Fog settings.
If you use dnsmasq as your PXE server, use d_nedelchev's advice, it is what you need.
But this will NOT have an impact on the DNS settings that DHCP server sends.
In my opinion, you should remove all DNS settings from the PXE server and keep only the DNS settings that the DHCP Server sends to clients.
Also, the PXE server should not send IP config (including DNS, gateway) etc., just the Network Boot Program name and location (tftp server), along with specific PXE/Fog settings.
If you use dnsmasq as your PXE server, use d_nedelchev's advice, it is what you need.
ASKER
Ok. I have set up proxyDHCP let me test it for a few days. Also where do I remove the DNS settings on the PXE server, dhcpd.conf?
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
What service acts as a proxyDHCP server ? dhcpd or dnsmasq ?
ASKER
Dnsmasq.
hi,
please see your dns enty in your dhcp.conf
and please send me dhcp.conf and dns cofiguration image.
please see your dns enty in your dhcp.conf
and please send me dhcp.conf and dns cofiguration image.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Note that binding dnsmasq to UDP 4011 is useful ONLY if a dhcp service runs on the same host (but it can't really be a problem from the server's point of view. Now, from the client point of view, this is another story and my article explains it all). See my article https://www.experts-exchange.com/Networking/Misc/A_2978-PXEClient-what-is-it-for-Can-I-use-PXE-without-it.html to understand why.
hi,
what is your actual problem,
1. fog server dhcp => if dhcp is in same host fog server ip enter in your dhcp file
2. dns => if dns not work please see your dns configuration( if this is in your system)
3. pxe boot => fog client always runs by pxe-boot for image store.
what is your actual problem,
1. fog server dhcp => if dhcp is in same host fog server ip enter in your dhcp file
2. dns => if dns not work please see your dns configuration( if this is in your system)
3. pxe boot => fog client always runs by pxe-boot for image store.
ASKER
Rajeev,
The problem id that fog dhcp was handing out dns settings (that didn't work) to clients that were not PXE booting.
d_nedelchev
netstat -apn | grep -i 'dnsmasq' output looks good. isc-dhcp-server is removed. But, after removing it, PXE clients get "TFTP open timeout."
The problem id that fog dhcp was handing out dns settings (that didn't work) to clients that were not PXE booting.
d_nedelchev
netstat -apn | grep -i 'dnsmasq' output looks good. isc-dhcp-server is removed. But, after removing it, PXE clients get "TFTP open timeout."
ASKER
Ok, problem solved. I had to uncomment "# enable tftp"
My ltsp.conf
My ltsp.conf
# 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=192.168.0.45,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,infiniteASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
Accidentally chose my own comment along with his.
ASKER
I guess that solved it.
To understand the interaction between PXE and DHCP servers, check my article and its comments:
https://www.experts-exchange.com/Networking/Misc/A_2978-PXEClient-what-is-it-for-Can-I-use-PXE-without-it.html