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Freeradius & DHCP Failover

05/30/11

  12:03:00 am, by The Dreamer   , 1362 words  
Categories: Software, Computer, Networking, WiFi, Ubuntu

Freeradius & DHCP Failover

Link: http://deployingradius.com/

During this work, the Airport Extreme listed options for two RADIUS servers. In one of the examples (for a different router), it said if you only have one RADIUS server...put its IP in for both. Well, I do have two Ubuntu servers...so it shouldn't be that hard to install it on the other server, 'Orac', as well. And, sync over the configs and give me redundancy. I was already sync'ng over my dhcp3-server configs there with the plan that someday I would have failover DHCP going. I had previously tried, but the servers were of different releases of Ubuntu...and therefore different versions of dhcp3-server, which meant it wouldn't work. So, I had commented things out. Plus I needed to reorganize the files so that dhcpd.conf would stay on each server, and the common part is sync'd between the two.

So, I cheated...a while back, I had peeked at that failover DHCP configuration at work and saw that it was a dhcpd.conf file on each server and it 'include's another file (which then includes much more...). So, I knew that I would eventually be doing something like this, so when I added the rsync for freeRADIUS...I updated the rsync of a different file than dhpcd.conf. For lack of a better name, I went with master.conf. Initially it was just a copy of my current dhcpd.conf, but dhcp3-server wasn't installed on 'Orac' yet...so the other pieces would wait.

I added a Makefile to /etc/freeradius to restart freeradius if either clients.conf or users got newer. freeradius could take HUP to see configuration changes, while dhcp3-server takes a restart and that's what the Makefile I was working on was original for.

So, having updated the rsync process and the Makefiles....I decided that I should really get dhcp failover going, before turning back to getting freeRADIUS working.

So, I created a new dhcpd.conf on 'box' and fired it up. Made some tweaks as it complained, and it seemed good. I do have a small DHCP range, but its a guest jail. Everything that matters is reserved. Well, at work, those 'host's are part of the 'subnet' declaration...with 'pool' at the top. But, when I restarted dhcp3-server on 'box', it warned me that the 'host' entries were global. Does that mean it doesn't really care in a failover situation? I had wondered if I really needed all this, but it wasn't clear what I had found online whether more than one dhcp server on the same network would get along even if there were no dynamic hosts. And, I'm still not really sure.

I then installed dhcp3-server on 'Orac', replaced the default dhcpd.conf with my secondary version of dhcpd.conf and had it include master.conf. It had tried to start, but failed, on install....had to tweak /etc/default/dhcp3-server....

And, then I tried to start it. I warned about "No subnet declaration for eth0 (192.168.1.10)." during the first start, and that it was "** Ignoring requests on eth0...." And, that it was "Not configured to listen on any interfaces!" Probably not what I wanted, eh? But, after a pause, it continued its startup....which included getting from my other DHCP server, the dhcpd.leases information. I looked at the configs, there's only one subnet defined..and its my entire network. So, it should've worked. I restart dhcp3-server and this time no message and all is happy. I guess it needed to talk the "failover peer" for the subnet before the subnet definition would be valid....

Later I saw that it was answering DHCPREQUESTs just as 'box' was...and things seemed to continue to work fine, and it would periodically rebalance the dynamic pool. I didn't realize how chatty some of my DHCP devices were. Namely my Nintendo 3DS. Doesn't seem to matter that default lease time is 24 hours, and max lease time is 7 days. I used to have both set to 2 weeks, but had lowered it because I thought some other device was having issues with long lease times. While, its the ReplayTV that didn't like short lease times...but there's only one in operation now...and I haven't touched it in months. I just records stuff, and people request shows from it...and I send them. No idea if the recording was good or not, though people usually tell me. I pretty much have no interest in watching SD if my TiVo fails to get something I want in HD. I'll go and seek out other sources first (Amazon Ondemand, NetFlix streaming, Amazon Prime Instant Video, Apple iTunes....) And, even if I do have to resort to SD...I don't watch it from my ReplayTV anymore....I'll opt for the extra work of transcoding it and sending it to a TiVo.

At one time, Cox had announced that they were going to bring ondemand to TiVo Premiere owners. I wonder what ever happened to that? :hmm:

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Now instead of subjecting some poor random forum to a long rambling thought, I will try to consolidate those things into this blog where they can be more easily ignored profess to be collected thoughts from my mind.

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