DHCP lease time question.

BlueMak · Nov 30, 2007, 04:15 AM

DHCP lease time to 24hours, does this mean my router will reboot or in any way stop the internet connection? Do you think if I change it to something more realistic for my PC usage, like 3 days, would it matter?

***temeteus82*** · Nov 30, 2007, 04:28 AM

nope, lease time is the time how long the DHCP server will lease the IP address to the computer/device using it. 24H is good lease time in DHCP servers configurations.

Tipstaff · Nov 30, 2007, 05:08 AM

In the corporate/business world, 24hrs is a good lease time. To the average consumer, maybe not. Really depends on the situation.

For instance, say you download a lot (ie. Torrent/eMule), or you do a lot of online gaming, and have your router setup to forward ports to your computer. In this instance you would want the lease time to NOT expire. While there's a good chance the router will assign you the same IP again if you were to reconnect to the router, there is always a chance it may not, and you may find it will assign you a different IP. In this case it would make more sense to change it to not expire.

If, however, you aren't doing any downloading, or playing online games, or pretty are using much anything that doesn't require specific ports to be forward (or that are NAT/UPNP capable), then having a short lease time isn't going to effect you.

***temeteus82*** · Nov 30, 2007, 05:24 AM

Quote:

Originally Posted by Tipstaff

For instance, say you download a lot (ie. Torrent/eMule), or you do a lot of online gaming, and have your router setup to forward ports to your computer. In this instance you would want the lease time to NOT expire. While there's a good chance the router will assign you the same IP again if you were to reconnect to the router, there is always a chance it may not, and you may find it will assign you a different IP.

I've found out that most of the home routers just let the IP be the same since they got full C-class subnet so there aren't really need to change the IP. And most routers keeps record of MAC addresses and IP assigned to them so that they would assign it again to that MAC address. But I personally use static manually configured IP address in my PC at home. Makes life easier if you know how to do it.

BlueMak · Nov 30, 2007, 09:00 AM

So, if I am downloading a file from say gamershell at the time, or some torrent, or I am in the middle of a multiplayer online game, will this be a problem like, connection lost thing?

***temeteus82*** · Nov 30, 2007, 09:57 AM

Quote:

Originally Posted by BlueMak

So, if I am downloading a file from say gamershell at the time, or some torrent, or I am in the middle of a multiplayer online game, will this be a problem like, connection lost thing?

Yes if the IP changes if it don't then you don't have problem. But I think you would not notice it since the change is done so fast that you cant see it. Perhaps some small lag on the game. as for torrent if you have port forwards in use then it might be too if the IP changes. If the router is UPNP compatible then you should see if the torrent client has support for UPNP since it can open the ports what your torrent client needs.

BlueMak · Nov 30, 2007, 10:03 AM

I am not sure what it has.
It is a Siemens CL-110.
My previous last router was one that I used briefly 3 years ago and it sucked cause no matter what I put in the DMZ all my games were getting blocked etc etc.
This one doesn't look it has any DMZ, but I have no problems yet with the couple of games that I have tried online...so, I don't know.

I guess one way to check will be to try to be online at the time.

***temeteus82*** · Nov 30, 2007, 10:19 AM

you got UPnP support in it and NAT so it would look like you don't need to use DMZ at all.

Matth · Nov 30, 2007, 10:54 AM

The TCP/IP Guide - DHCP Lease "Life Cycle" Overview (Allocation, Reallocation, Renewal, Rebinding and Release) and Lease Timers

Renewal is attempted when the lease is half expired, and unless something has happened to force a change, the same address will normally be renewed.

If the lease time is too long, this can cause problems, if the client device is still holding the lease (before T1) and the router has been turned off and has lost it's cache of issued leases - the next client will often suffer a collision.

The way to resolve those collisions, is to release addresses on all devices and allow the DHCP process to issue new leases. Using fixed addressing is another option, either fixed client IP, or fixed hardware address to IP mapping if the router supports it.

Judas · Nov 30, 2007, 01:30 PM

quite a number of cheaper routers typically don't have an option to change lease time... or don't have one at all really. they usually just keep handing out the same ip to the same mac address everything single time reguardless of what you do (enless you forcefull set one)

For example, the dlink/linksys/netgear/airlink/SMC routers i've delt with wired or wireless.... reguardless of the connection, guaranteed nearly all the time, once you've gotten a specific adapter to connect to it once, forever the router will give it the same ip.

Now the more expensive ones usually set up a better dynamic ip system. In which case you have to manually input your network adapters MAC address directly into the router and specify an ip that you want to give it, while for most users, it's not nessary, but in the case of wanting to port forward or host a server of any type, you HAVE to do this or else you'll find yourself constantly having to readjust the port forwarding.

My xincom 502 twin wan router allows me to set the dhcp lease times from as low as i beleive 1 minute (no good) to 1440 minutes (i think i could go larger since the routers firmware update recently)

1440 minutes is exactly 24 hours...

quite often if i didn't force a ip/mac address to a static form, within a 24 hour period.... the ip would suddenly change.. and anyone that wanted to connect to my server would be disallowed until i changed it again.

BlueMak · Nov 30, 2007, 03:17 PM

Well it looks l ike the half time thingy worked on its own. I checked earlier to see if I have 12-13 hours left and instead I had about 19 hours left.
Now I have to find a way to be there the next time it happens.

kn00tcn · Dec 4, 2007, 11:21 PM

i skimmed but if you dont restart the computer, the ip stays the same

for me, i got 2 desktops & a laptop, with a 1440min default lease time, but also 3 MAX dhcp clients... now my desktops are always on so their ip never changes, & then the laptop comes on from time to time & gets the remaining slot... basically, i've never had any of my IPs change in all the time i've had this router (september-now)

& even with changing IPs, just use UPnP if possible to auto open ports (no it's not a massive security risk if you know what processes run on your OS+check tcp connections once in a while)

BlueMak · Dec 5, 2007, 02:05 AM

Nah, I stopped trying to be there when it happens. Also I don't really care for IP changes (I don't have a server running or anything), so I just gave up on finding out what happens.

The connection is fine, it only goes up to 14mbps, but that is still plenty fast for me. Downloading a GB in a few min is fine.

The only thing I don't like and not sure what is causing it or how to solve it is that some times when I try to check a site I get nothing and I have to click again or refresh the page for it to load.

kn00tcn · Dec 5, 2007, 07:05 PM

that could be related to the tcptimeout options in the router

BlueMak · Dec 6, 2007, 03:57 AM

Hmm, care to explain that a bit please?

Liqourice · Dec 6, 2007, 02:21 PM

Is there really any advantage using DHCP instead of static IP's in your home router?

I've always set static IP's, mostly because I have a webserver at home and because of the less hassle with port forwarding if the IP should change.

***temeteus82*** · Dec 6, 2007, 02:32 PM

I would say yes. Since if you have laptops that are using WiFi then it would be better to have the DHCP running.

H3X4D3C1M4L · Dec 22, 2007, 07:04 PM

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6 - Networking

And if you really want to learn about how these things work and which is better and why... this is all you'll ever need.

http://www.3com.com/other/pdfs/infra..._US/501302.pdf

Its a long read but it was way worth it and I can highly reccomend it.