Menu
▾
▴
Re: [Packetfence-devel] DHCP leases
|
From: Eric K. <xn...@gm...> - 2006-09-06 17:43:42
|
Bear with me, this is all being pulled from my head and I haven't looked into aspects of this in going on a year.... Also this doesn't have anything to do with how PF might do things, this is all just on DHCP in general. This would only slightly decrease your network traffic. Assuming the machine isn't rebooted in 30 days, and your lease time is set for 30 days, 15 days into it (half the life of the lease) the machine would still request to renew its lease. Assuming it doesn't get a response from the DHCP server, 7.5 days later it will request again, again assuming it doesn't get a response it will turn around and request to renew the lease 3.75 days later, and on and on until it either gets a renewel on the lease or it fails. If it fails then every few mins, once the lease is expired it will continue to do a DHCP Discover and DHCP Request. Depending on your enviornment you may also get DHCP Inform packets throughout the day from different clients. Assuming you have the Netware 32 bit client installed you will see about 3 different kinds of INFORM packets, I've never tracked down how often they show up, but at least in our enviornment they popup from time to time. Again, so far this all assumes that the computer in question never is rebooted. Otherwise, if it is rebooted, each time it boots it will at least do a DHCP Request and normally DHCP Discover (some older OS's seemed to only do one upon logging into the workstation (Windows 95 for example)). I would say it all depends on the number of IPs you have in your DHCP pool and the number of hosts you expect. While at my last place of employment we had approximately 550 workstations with only 450 IP addresses in the DHCP pool, so the DHCP lease time was set extremely low (a few hours). Since we were a 24 hour shop and laptops came and went this normally wasn't an issue, but did add to the traffic. On the other hand, at the university I'm back at now I think we typically do a 7 day lease on our wired network and a 24 hour lease on our wireless one. Someone may have a good algorythm on the best way to set all this up, but from what I've seen, network traffic wise, you probably aren't saving much more than a few packets. (normal DHCP process is what, 4 packets? DHCP Discover, DHCP Ack, DHCP Request, DHCP Inform, plus a few ARP packets depending on OS to verify that that IP is free from both the DHCP server and the Client Workstation). Again, this is all from a DHCP perspective as a whole, not with PF involved at all, since I haven't dug into how it does anything and where their might be good reasons to make it longer or shorter. Eric On 9/6/06, David Rickard <da...@da...> wrote: > > Hi, > > This is a related-unrelated question. > > I'm wondering about DHCP lease lengths. I'm looking to use roughly a > month, so as to stick users in one place, but not too long that the > leases don't clean out too slowly. It also keeps traffic down, as DHCP > can be a bit chatty in my experience! I'm wondering if there's a 'sweet > spot' timeout to use? Any words of wisdom from Dave or Kevin perhaps? > > I'm wondering if the lease length matters depending on the type of > deployment in use. In theory it shouldn't, but you never know! We all > know how fickle computers can be! > > Regards > -- > > _ > David Rickard ASCII ribbon campaign ( ) > da...@da... - against HTML email X > www.davidrickard.net & vCards / \ > > ------------------------------------------------------------------------- > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job > easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Packetfence-devel mailing list > Pac...@li... > https://lists.sourceforge.net/lists/listinfo/packetfence-devel > |