problems with having two DHCP servers...
On 12/27/11 22:04, Scott Ferguson wrote: It sounds like you are running two DHCP servers - in which case you have four options (none of which involve preseeding). If you have multiple DHCP servers the problem is *easily* fixed - please tell me the make and model of the primary (router/firewall) DHCP server and I'll give you instructions. Hi Scott, I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Both DHCP servers are dnsmasq. When I kill off one of the servers temporarily, all goes well. Is there a solution that isn't so drastic? Thanks! Rick -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4f056cbc.3090...@pobox.com
Re: problems with having two DHCP servers...
Hi On Thu, Jan 05, 2012 at 04:26:20AM -0500, Rick Thomas wrote: On 12/27/11 22:04, Scott Ferguson wrote: It sounds like you are running two DHCP servers - in which case you have four options (none of which involve preseeding). If you have multiple DHCP servers the problem is *easily* fixed - please tell me the make and model of the primary (router/firewall) DHCP server and I'll give you instructions. Hi Scott, I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? Both DHCP servers are dnsmasq. Why having 2 in a network. Keeep them separated is the way to go. When I kill off one of the servers temporarily, all goes well. I thought this is the right solution. Is there a solution that isn't so drastic? Make a sane network configuration, I think... Osamu -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20120105150747.GA7425@localhost
Re: problems with having two DHCP servers...
A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. Rick On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote: I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/d73b70b2-c677-4de4-a722-3606ae535...@pobox.com
Re: problems with having two DHCP servers...
On Thu, 2012-01-05 at 12:57 -0500, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. Rick On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote: I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? The problem is when they are administering addresses in the same range. I've not configured DHCP for a long time so maybe this is common now and the problems have all been resolved but, in the past, if one wanted redundancy, one would administer different ranges on the same subnet so that there would be no conflicts. Hope that helps - John -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1325788823.7219.168.ca...@denise.theartistscloset.com
Re: problems with having two DHCP servers...
On 06/01/12 06:57, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. My understanding is that you need to have some sort of failover setup - so the secondary dhcp server only starts working (responding) if it detects that the first has failed. It also needs to track all the leases that the first has handed out, so it can avoid issuing duplicates. I haven't looked at this in detail, though. Richard -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4f060ff5.9050...@walnut.gen.nz
Re: problems with having two DHCP servers...
On Jan 5, 2012, at 1:40 PM, John A. Sullivan III wrote: On Thu, 2012-01-05 at 12:57 -0500, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. Rick On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote: I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? The problem is when they are administering addresses in the same range. I've not configured DHCP for a long time so maybe this is common now and the problems have all been resolved but, in the past, if one wanted redundancy, one would administer different ranges on the same subnet so that there would be no conflicts. Hope that helps - John Yes, that does seem to fit. The two servers have different ranges for their dynamic clients (i.e. transient laptops with no fixed IP address) but for the static clients (desktops with a fixed IP address) there is only one address, so both servers have to provide the same address. So... when I do an install for a machine with an unknown Ethernet Mac address -- hence getting it's IP from one or another of the dynamic ranges -- all goes well. It's only when I attempt to install a machine with a known Mac address (hence a single static IP) that I run into trouble. Somehow, I would have thought it should be the other way round -- conflicting responses would cause problems, not two responses that both say the same thing. Sigh! Just shows how much I know... So is there a way to have both redundancy *and* reliable installs? Thanks for any help, Rick PS: As others have noted, it seems to affect only the installer's DHCP client. After the reboot, there's no problem -- with either static or dynamic IP... -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/cbe291f4-f733-4eed-9cb3-6d62732e1...@pobox.com
Re: problems with having two DHCP servers...
On Fri, 06 Jan 2012 10:02:45 +1300, Richard wrote in message 4f060ff5.9050...@walnut.gen.nz: On 06/01/12 06:57, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. My understanding is that you need to have some sort of failover setup - so the secondary dhcp server only starts working (responding) if it detects that the first has failed. It also needs to track all the leases that the first has handed out, so it can avoid issuing duplicates. ..you also need to decide on your policy issues, e.g. on whether you want your downed primary server taking over as the primary once it's up again, or whether it should take over as secondary|spare until your secondary goes down, etc, etc. Etc. I haven't looked at this in detail, though. ..about 8 years since I did. ;o) -- ..med vennlig hilsen = with Kind Regards from Arnt Karlsen ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20120105221711.3ee35...@nb6.lan
Re: problems with having two DHCP servers...
On Thu, 2012-01-05 at 15:55 -0500, Rick Thomas wrote: On Jan 5, 2012, at 1:40 PM, John A. Sullivan III wrote: On Thu, 2012-01-05 at 12:57 -0500, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. Rick On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote: I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? The problem is when they are administering addresses in the same range. I've not configured DHCP for a long time so maybe this is common now and the problems have all been resolved but, in the past, if one wanted redundancy, one would administer different ranges on the same subnet so that there would be no conflicts. Hope that helps - John Yes, that does seem to fit. The two servers have different ranges for their dynamic clients (i.e. transient laptops with no fixed IP address) but for the static clients (desktops with a fixed IP address) there is only one address, so both servers have to provide the same address. So... when I do an install for a machine with an unknown Ethernet Mac address -- hence getting it's IP from one or another of the dynamic ranges -- all goes well. It's only when I attempt to install a machine with a known Mac address (hence a single static IP) that I run into trouble. Somehow, I would have thought it should be the other way round -- conflicting responses would cause problems, not two responses that both say the same thing. Sigh! Just shows how much I know... So is there a way to have both redundancy *and* reliable installs? Thanks for any help, Rick PS: As others have noted, it seems to affect only the installer's DHCP client. After the reboot, there's no problem -- with either static or dynamic IP... Hmm . . . could you install with a manual IP address and then simply change the configuration once the installation is done? - John -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1325799032.7219.190.ca...@denise.theartistscloset.com
Re: problems with having two DHCP servers...
John A. Sullivan III wrote: The problem is when they are administering addresses in the same range. I've not configured DHCP for a long time so maybe this is common now and the problems have all been resolved I believe the problem is sufficiently resolved now. Time has past and this is definitely something where improved code has improved the situation quite a bit. but, in the past, if one wanted redundancy, one would administer different ranges on the same subnet so that there would be no conflicts. I think the best in class solution available today is to use the ISC DHCP daemon. This is packaged for Debian as isc-dhcp-server. Then configure two machines in a failover configuration. This works very well. I am doing this on a variety of sites. It is very robust and works great. Sometimes people curse it though due to a self-inflicted configuration problem. I have seen people try this repeatedly for some reason. And I have a hard time understanding why. They try to use half as many IP addresses in the pool as they need. I don't know why but they do. There are a *lot* of addresses available from the RFC1918 private ranges and even on large networks I have a hard time conceiving of being short of IP addresses. But people seem to often configure only half as many addresses as they need. Then when one server is offline the remaining server, which is working perfectly as configured, runs out of IP addresses to assign because the pool is only half as large as it should be in order to support the network. I think people hit this case because when both servers are up and online they effectively have load sharing and so each has 50% of their pool free. So they use a pool that is too small because they are fooled into thinking of the case with both servers running instead of thinking of the case of a server being disconnected. But it is the disconnected case that is the important one! The simple solution is very simple. Use a large enough pool and this problem is avoided. Bob signature.asc Description: Digital signature
Re: problems with having two DHCP servers... (Rick Thomas)
On 05/01/12 20:26, Rick Thomas wrote: On 12/27/11 22:04, Scott Ferguson wrote: It sounds like you are running two DHCP servers - in which case you have four options (none of which involve preseeding). If you have multiple DHCP servers the problem is *easily* fixed - please tell me the make and model of the primary (router/firewall) DHCP server and I'll give you instructions. Hi Scott, I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Both DHCP servers are dnsmasq. When I kill off one of the servers temporarily, all goes well. Is there a solution that isn't so drastic? Thanks! Rick Hi Rick - sorry about the delayed reply, I've been busy. I've had a quick look at the thread and I've a few questions before I make any suggestions. Q1. Is there any functionality only one of your DHCP servers[*1] can provide eg. wireless connection. Q2. What is the maximum number of clients you are ever likely to have connected to the networks serviced by these DHCP servers. Q3. Do you use PXE/GPXE/RIS? Q4. If either of these DHCP servers doesn't run Debian - what is/are the make and model/s? Q5. If either of these DHCP servers run FOSS - what is the DHCP package? [*1] I noted your intention of having a backup/failover DHCP server - I'd probably suggest a different way of doing that, but I'll wait on some answers first. Cheers -- Iceweasel/Firefox extensions for finding answers to Debian questions:- https://addons.mozilla.org/en-US/firefox/collections/Scott_Ferguson/debian/ -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4f06482d.60...@gmail.com
Re: problems with having two DHCP servers...
On 01/05/12 16:30, John A. Sullivan III wrote: On Thu, 2012-01-05 at 15:55 -0500, Rick Thomas wrote: On Jan 5, 2012, at 1:40 PM, John A. Sullivan III wrote: On Thu, 2012-01-05 at 12:57 -0500, Rick Thomas wrote: A limited amount of redundancy is good. If one goes down, the network can still limp along. Anyway, that's the theory. Rick On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote: I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Then why have 2? The problem is when they are administering addresses in the same range. I've not configured DHCP for a long time so maybe this is common now and the problems have all been resolved but, in the past, if one wanted redundancy, one would administer different ranges on the same subnet so that there would be no conflicts. Hope that helps - John Yes, that does seem to fit. The two servers have different ranges for their dynamic clients (i.e. transient laptops with no fixed IP address) but for the static clients (desktops with a fixed IP address) there is only one address, so both servers have to provide the same address. So... when I do an install for a machine with an unknown Ethernet Mac address -- hence getting it's IP from one or another of the dynamic ranges -- all goes well. It's only when I attempt to install a machine with a known Mac address (hence a single static IP) that I run into trouble. Somehow, I would have thought it should be the other way round -- conflicting responses would cause problems, not two responses that both say the same thing. Sigh! Just shows how much I know... So is there a way to have both redundancy *and* reliable installs? Thanks for any help, Rick PS: As others have noted, it seems to affect only the installer's DHCP client. After the reboot, there's no problem -- with either static or dynamic IP... Hmm . . . could you install with a manual IP address and then simply change the configuration once the installation is done? - John Of course. And that's exactly what I usually wind up doing. Though now that I've discovered that temporarily killing one of the dhcp servers works, I may do more of that in the future. Really, I'm mostly interested in figuring out what's going on and probing to help get it fixed. Enjoy! Rick -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4f064899.6020...@pobox.com
Re: problems with having two DHCP servers...
On Thu, 2012-01-05 at 20:04 -0500, Rick Thomas wrote: On 01/05/12 16:30, John A. Sullivan III wrote: snip Hmm . . . could you install with a manual IP address and then simply change the configuration once the installation is done? - John Of course. And that's exactly what I usually wind up doing. Though now that I've discovered that temporarily killing one of the dhcp servers works, I may do more of that in the future. Really, I'm mostly interested in figuring out what's going on and probing to help get it fixed. snip That makes sense. In that case, I would suggest putting a protocol analyzer on the line and see what is happening on the wire - John -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1325818568.7219.191.ca...@denise.theartistscloset.com
Re: problems with having two DHCP servers...
John A. Sullivan III wrote: Rick Thomas wrote: Really, I'm mostly interested in figuring out what's going on and probing to help get it fixed. snip That makes sense. In that case, I would suggest putting a protocol analyzer on the line and see what is happening on the wire - John I have had good luck using the 'dhcpdump' program for that purpose. It is simple and direct and packaged for Debian. Bob signature.asc Description: Digital signature
Re: problems with having two DHCP servers... (Rick Thomas)
On 01/05/12 20:02, Scott Ferguson wrote: On 05/01/12 20:26, Rick Thomas wrote: On 12/27/11 22:04, Scott Ferguson wrote: It sounds like you are running two DHCP servers - in which case you have four options (none of which involve preseeding). If you have multiple DHCP servers the problem is *easily* fixed - please tell me the make and model of the primary (router/firewall) DHCP server and I'll give you instructions. Hi Scott, I'm not the OP, but I do have this problem. When I try to do an install (wheezy) on a network with two DHCP servers, the installer's dhcp-client never seems to get an IP address -- even though the two servers are both responding and both giving the same IP address. Both DHCP servers are dnsmasq. When I kill off one of the servers temporarily, all goes well. Is there a solution that isn't so drastic? Thanks! Rick Hi Rick - sorry about the delayed reply, I've been busy. I've had a quick look at the thread and I've a few questions before I make any suggestions. Busy happens. Thanks for getting back in any case. Q1. Is there any functionality only one of your DHCP servers[*1] can provide eg. wireless connection. They are essentially identical. Both are SheevaPlug ARM based plug-computers. I'm researching using cheap boxes like these (running Debian) to provide network services. I hope to show that one can use free software and very inexpensive energy-efficient general-purpose hardware do full-up network support (DHCP, DNS, TFTP booting, NIS, Kerberos, printer spooling, NTP, network monitoring, etc...) for much less money than conventional IT costs using commercial purpose-built routers. Redundancy and load-sharing are important parts of the strategy. Q2. What is the maximum number of clients you are ever likely to have connected to the networks serviced by these DHCP servers. In my test network, I don't expect to have more than 15-20 clients. In the eventual fully deployed system, I could be providing services to well over a 1000 clients. Here, redundancy and load-sharing will become crucial. Q3. Do you use PXE/GPXE/RIS? Not yet. it's in the plans though. Right now, I'm concentrating on DHCP and DNS service. Q4. If either of these DHCP servers doesn't run Debian - what is/are the make and model/s? See Q1. SheevaPlug, running Debian Squeeze. Q5. If either of these DHCP servers run FOSS - what is the DHCP package? Running dnsmasq providing DHCP and DNS [*1] I noted your intention of having a backup/failover DHCP server - I'd probably suggest a different way of doing that, but I'll wait on some answers first. Does that help? Thanks! Rick -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4f0688e4.9040...@pobox.com
