Ubuntu Networking :: If DHCP Not Available - Fallback And Start DHCP Server?
Mar 8, 2010
Currently I have my eth0 interface getting a DHCP address but at times the DHCP server will not be reachable. Sooo what I would like my server to do is if it cannot find a DHCP server assign a static address to eth0. Then start the DHCP service so it can then dish out some addresses.How can I do this? Surely it is possible
I have a home network, with an OpenWrt router operating successfully as DHCP server (using DNSMasq). I'm planning to install LinuxMCE on my main fileserver and in order for this to properly detect devices around the home it requires that it is the DHCP server. That would be fine except that I sometimes power down the fileserver (eg. when my in-laws sleep in the spare room where the server lives) and that would leave me with no DHCP which creates problems (when my in-laws want to get their laptop connected to the internet).
One answer is to get new in-laws which would be OK except that I'm still pretty keen on my wife. Alternatively is there any way to set up a fallback DHCP server ie. the router would check if there's a functioning DHCP server on the network (ie. the fileserver) and if it gets no response it will serve DHCP addresses itself.
Back in April I set up a Ubuntu DHCP server and a multiple VLAN network [URL] to migrate our various servers, workstations, etc off the 192.168.1.1 /24 network that everything was on because we where running out of address space. I built out the new network and everything worked great except our AD server would never get an IP address from the DHCP server (static reservation) and even if I set the IP statically on the AD server it couldn't ping the gateway and noone could log in. After several attempts to resolve this, including bringing in outside help, we where never able to figure out what the problem was.
Now 6 months later I have time to revisit the issue without effecting the live network. I used Acronis and imaged the AD server last Friday, cloned it on to another box with the same hardware, and put it up on the new network that's been sitting unused for the last 6 months. Today when I statically set the IP on the AD server (which is what I want) it connects and I can ping it's gateway 192.168.1.1 and all the way across vlans to a test sales agent workstation at 192.168.8.xxx on vlan 800 but only if I statically assign the agents station an IP address. When I try to get an IP address via DHCP it fails as destination unreachable. Nothing has changed in the last 6 months on the DHCP server but now it for some reason can't ping its default gateway 192.168.1.1. All of the config files are the same as they where left from the post linked above aside from the vlan id's used where changed from 1's to 100's (i.e. vlan 3 is now vlan 300) /etc/network/interfaces
Code:
auto lo iface lo inet loopback auto vlan100 iface vlan100 inet static
[code]....
why it can't reach the gateway, when I do a tcpdump I can see the DHCP requests come in on eth0 but the server never responds and I'm pretty sure its because it isn't "seeing" them since it thinks there isn't a network connection but I don't know how to trouble shoot to find out where the problem lies.
Back in April I set up a Ubuntu DHCP server and a multiple VLAN network [URL] to migrate our various servers, workstations, etc off the 192.168.1.1 /24 network that everything was on because we where running out of address space. I built out the new network and everything worked great except our AD server would never get an IP address from the DHCP server (static reservation) and even if I set the IP statically on the AD server it couldn't ping the gateway and noone could log in. After several attempts to resolve this, including bringing in outside help, we where never able to figure out what the problem was.
Now 6 months later I have time to revisit the issue without effecting the live network. I used Acronis and imaged the AD server last Friday, cloned it on to another box with the same hardware, and put it up on the new network that's been sitting unused for the last 6 months. Today when I statically set the IP on the AD server (which is what I want) it connects and I can ping it's gateway 192.168.1.1 and all the way across vlans to a test sales agent workstation at 192.168.8.xxx on vlan 800 but only if I statically assign the agents station an IP address.
When I try to get an IP address via DHCP it fails as destination unreachable. Nothing has changed in the last 6 months on the DHCP server but now it for some reason can't ping its default gateway 192.168.1.1. All of the config files are the same as they where left from the post linked above aside from the vlan id's used where changed from 1's to 100's (i.e. vlan 3 is now vlan 300) /etc/network/interfaces
Code:
auto lo iface lo inet loopback auto vlan100
[code]....
why it can't reach the gateway, when I do a tcpdump I can see the DHCP requests come in on eth0 but the server never responds and I'm pretty sure its because it isn't "seeing" them since it thinks there isn't a network connection but I don't know how to trouble shoot to find out where the problem lies.
I am puzzled with trying to configure a linux (openSUSE) client to dhcp to eBox DHCP server. I am using dhclient to lease an IP address with dhclient eth0 -s 10.45.48.108 and get a response
openSUSE11232CL1 dhclient: DHCPDISCOVER on eth0 to 10.45.48.108 port 67 interval 4 openSUSE11232CL1 dhclient: DHCPOFFER from 10.45.48.108 openSUSE11232CL1 dhclient: DHCPREQUEST on eth0 to 10.45.48.108 port 67 openSUSE11232CL1 dhclient: send_packet: Network is unreachable openSUSE11232CL1 dhclient: send_packet: please consult README file regarding broadcast address.
The server reports eBox141 dhcpd: DHCPDISCOVER from 00:0c:29:3e:57:a3 (openSUSE11232CL1.domain.net) via eth0 eBox141 dhcpd: DHCPOFFER on 10.45.200.2 to 00:0c:29:3e:57:a3 (openSUSE11232CL1.domain.net) via eth0
I interpret this as the server receives the request and the client accepting it but the lease does not last long and the connection breaks. what this could be and why the connection breaks? Or my undestanding is totally wrong on how it works and should work? And BTW, where is that README file that's referenced in the message I receive on the client?
I have an embedded device for which I've created an html configuration page. This page allows you to set static IPs, dhcp, and can scan for wireless devices.My problem is that in order to access the device it requires that it runs as a dhcp server otherwise people are not assigned an IP and so can not access the embedded devices static IP. (This config page is for the laymen and so they are not the type who are able to set up their own static IPs). One of the potential options is to have the device connect to the network on eth0 acting as a dhcp client. However this prevents me from running a dhcp server.One solution I can think of is running a dhcp server only if it doesn't detect another dhcp server running on the network.
This dhcp server is configured with redhat enterprise edition. I found that logs are generating in the following path /var/log my doubt is how can i setup the logs generating for a specified day.
I have Centos 5 installed on a PC in the local network. I have installed the RPM dhcpv6-client-1.0.10-16.el5.i386.rpm on this PC to configure it as DHCP V6 client. The RPM was installed successfully, and I have done modifications to the following files:
1. /etc/sysconfig/network, set the networking to yes. 2. /etc/sysconfig/network-scripts/ifcfg-eth1 set the BOOTPROTO=DHCP.
Now the problem is when I start the client on this pc as dhclient, it throws the following errors, and logs out after some time. All the network configurations were lost and the PC gets disconnected from the network.
[root@ServerB]# dhclient Internet Systems Consortium DHCP Client V3.0.5-RedHat Copyright 2004-2006 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/
first: PXE flawless bind to dhcp address but put next binding state to free second: when installer calls init script to reinit ethernet driver (e1000 (vmware)) binding fails 11.2 opensuse fail to reinit dhcp with log entry "no free leases" third: when manual set network install works how to preserve dhcp lease on reinit of driver?
I have an embedded device for which I've created an html configuration page. This page allows you to set static IPs, dhcp, and can scan for wireless devices. My problem is that in order to access the device it requires that it runs as a dhcp server otherwise people are not assigned an IP and so can not access the embedded devices static IP. (This config page is for the laymen and so they are not the type who are able to set up their own static IPs). One of the potential options is to have the device connect to the network on eth0 acting as a dhcp client. However this prevents me from running a dhcp server. One solution I can think of is running a dhcp server only if it doesn't detect another dhcp server running on the network. However I have no idea how this could be setup.
I have 2 Ethernet connections, one (eth0) for the internet which gets set with dhcp, and one (eth1) for my internal network on which I have dhcp3-server running. I set eth1 to use static IP in interfaces, but every time I reset the network, it is fine for a couple of minutes, and switches over do being served by my own dhcp server on the same machine. (the interfaces file clearly says "iface eth1 inet static")
I reinstalled Ubuntu server, now, as always I have to start off with 8.04 then upgrade to 10.04, and I've never had a problem with this before on this machine or any other for that matter. The problem is, this time I have installed and Ubuntu installer cannot see a DHCP, I go a head and install anyway and fire up Ubuntu and there is no internet access, I have two network cards plugged in, when I type in ifconfig it shows only lo and no network cards, and yet when I check lspci ot shows both network cards are there and when either are plugger in it shows connection on both the connector at the stack end and on the router.
i have a homework where i have to set up a dhcp server on linux. I am using ubuntu. I tried following: [URL] However after running "sudo apt-get install dhcp3-server" the file "/etc/default/dhcp3-server" does not appear.
I'm trying to build a linux(fedora 12) dhcpd server(and gateway), that have 3 network cards(eth0 have with public ip, eth1 192.168.2.1 class and eth3 with 192.168.3.1 class).
Because I have just a switch, I want to put both cables(from eth1, eth2) in the switch. Every client has 2 network card(eth0, eth1). My question is, is there any way to conf eth0 to take from server ip from 192.168.2.1 class, and eth1 from 192.168.3.1? The internet will work only on eth0.
I'm trying to get a dhcp server running on my laptop. I want devices to be able to connect to a wireless AP I've set up (using hostapd) to then connect to the rest of the internet via my ethernet connection from the laptop.
However, I can't get dhcp to work properly. It always fails, leaving this message in the syslog
Code: Jan 19 15:49:15 lucid-laptop dhcpd: WARNING: Host declarations are global. They are not limited to the scope you declared them in. Jan 19 15:49:15 lucid-laptop dhcpd: WARNING: Host declarations are global. They are not limited to the scope you declared them in.
I have a MacBook Pro running VirtualBox with Ubuntu 10.10 as a guest. I am trying to run a DHCP server from within the Ubuntu VM. I need to do this in order to run a multicast utility. On a stand alone machine running Fedcora I have this working without fail but within the Ubuntu VM I am having troubles. The DHCP server is starting okay, but when I use a cross over cable connected to a device the device does not ever get an address.I have eth1 bound to my ethernet jack where I am trying to source the addresses, and eth2 bound to my airport which is disabled unless I need internet access.Here is my DHCP.conf file
My Ubuntu server is now providing routing duties to my network, but I'm having trouble opening ports to my network. I have a DynDNS account, so the IP is always current, but I can't ping even my IP directly.
My network map looks like
Internet > SpeedTouch DSL modem with DHCP > eth1 > Ubuntu > eth0 > LAN
With the modem providing a 192.168.1.xx IP to eth1, I can browse fine. The default gateway is my modem. I switched to the public IP of the modem so I could use iptables for firewall duties, but I was locked out of the internet. No gateway was set when I did that, but eth1 received the public IP of my modem.
We have a network of 20 boxes and the router dealt with DHCP, but I'm planning to assign the DHCP task to the linux box. Any heads up? eth card configuration, network topology... etc.?
This is probably an odd request, but figured I'd ask in case someone knew. We have a lab that has the IP range 172.10.0.0/16 (255.255.0.0). The lab gateway/DHCP assigns an IP in the range of 172.10.0.2-172.10.0.254. I want to set up my own DHCP server on a specific range, for example 172.10.10.1-172.10.10.254. I create a new host fine, but since it's set for DHCP, it uses the DHCP server at 172.10.0.1. Is there a way to force it to use a different DHCP server on the client side? I realize that I can work around this with exclusions on the 172.10.0.1 DHCP server, or use iptables to deny DHCP requests to specific MACs, but wanted to know if there was an (easier?) way to configure the client to use the 172.10.10.1 DHCP server instead of the 172.10.0.1 server?
I have a scenario where a Debian (in this case) device will be connected to an existing LAN.What I then want said box to do, is to query the LAN to see if there is an existing DHCP server present. If there isn't one - then simply use the Debian box as the DHCP server (which works fine atm).If there is an existing one - I need the Debian box to be able to turn off it's own internal one and get it's details from the existing server (ie. change from server to client).
These action will need to be sat in the background as well - just in case another DHCP server appears on the LAN after this box does. Don't shoot me for saying it - but I know Windoze server does this. Is there a 'script/util' that anyone knows of (I am trying to do this auto-magically)?
when the machine rebooted, eth0 has the ip address 192.168.24.234. But if executing 'dhclient', eth0 will get the ip address 10.200.34.208, which is my expected ip address. I'm not quite familiar with networking things. I don't know what's going on there. Why should I need to execute 'dhclient' to obtain the expected ip address? Is there any way to obtain the ip address 10.200.34.208 right after host boot?
If I use static TCP configuration, (my Linux is Red Hat, but SuSE is quite similar) I define DNS's in file "/etc/resolv.conf" and Default GateWay in file
So, when I want to display those values, I just display the contents of the file. But, if my TCP configuration uses DHCP server ... I dont know the command to display those values. PD.- in straight : I need a command to display the DNS's in effect on a TCP/IP configuration that uses a DHCP server. Also, a command to display Default Gateway would be welcome.
I have installed Centos 5 on a virtual machine (esx4i). I set it to obtain an IP address from the DHCP sever, which is a broadband router, it has been given an IP address of 10.10.11.159 the router is 10.10.11.1 but I can't ping the router and I can't get any access to the network! I have a SCO Openserver server on the same physical box and it works fine so I know the network card & cable is ok.
I've noticed something strange in the behavior of how Ubuntu server obtains it's IP address versus Ubuntu desktop and other versions of linux and Windows. When Ubuntu desktop obtains an IP address from my router that address is retained from one bootup to the next, same behavior as Windows, SuSE, and pretty much any other OS. Ubuntu server on the other hand grabs a different IP address everytime it boots. At first I guessed it was a difference in /etc/dhcp3/dhclient.conf so I replaced it with the dhclient.conf from Ubuntu desktop but no dice, it still grabs a new address every time.
In /etc/network/interfaces Ubuntu server defines the loopback interface and primary network interface, just as it should but Ubuntu desktop does not define the network interface, only the loopback interface. I'm guessing something else controls does this. Desktop appears to be storing previous IP lease information in /var/lib/dhcp3/dhclient.eth0.leases but server doesn't, /var/lib/dhcp3/dhclient.leases is always empty and there's no other files in /var/lib/dhcp3/.
Apparently something isn't writing old lease info there. Without setting a static IP address, how can Ubuntu server be configured to retain the same IP address between boots like Ubuntu desktop?I'm using Ubuntu server 8.04LTS, Ubuntu desktop 9.10 & 9.04, SuSE 11.0, Linux Mint, Windows XP, pfSense 1.2.2 as router.
i already have an eth0 configured to automatically get its info from dhcp.
but i wanna configure eth1 to be able to serve dhcp and dns. i havent configured either dns or dhcp server on the server box since i have not configured the serving interface.
so far my interfaces file is:
Code: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp