[TelstraClear] ADSL 30 second DHCP lease

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mentalinc

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#55443 4-Jan-2010 18:59

Just wondering the reasoning behind having a 30 second DHCP WAN lease time?

I have a RTA1320 -> WRT running Tomato.
This sends a renew request every 15 seconds.
Its about 80MB a month just for DHCP (send and receive) seems kinda weird.

logs look like this for pages and pages
Jan 4 18:48:21 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:48:21 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:48:36 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:48:36 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:48:51 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:48:51 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:49:06 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:49:06 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:49:21 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:49:21 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:49:36 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:49:36 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:49:51 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:49:51 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:50:07 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:50:09 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:50:24 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:50:24 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:50:39 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:50:39 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30
Jan 4 18:50:54 Tomato daemon.info udhcpc[325]: Sending renew...
Jan 4 18:50:54 Tomato daemon.info udhcpc[325]: Lease of xxx.xxx.xxx.xxx obtained, lease time 30

Thanks

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cr250bromo

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#287024 4-Jan-2010 22:22

This is the way half bridge works... The dhcp lease time is kept short so that if your ip changes or you get disconnected the ip your wrt has can be updated without too much delay. It is your dsl modem enforcing this lease time.

You will not be billed for that traffic as it is only between the dsl modem and your wrt.

Ragnor

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#287035 4-Jan-2010 22:49

If your ADSL line drops or reconnects (for whatever reason) and you do not have a static ip address from your ISP then your ISP will normally assign you a different external/wan ip address.

Assuming you are using PPPoA half bridge (called ip extension in the Dynalink) to connect the two devices (in order to avoid double NAT) the RTA exposes the wan ip address to the WRT via DHCP for use as the wan ip address in the WRT.

Basically when your isp assigned ip address changes the WRT will not pick up the change from the RTA until the DHCP renews.

The lower the lease the less "downtime" when your external/wan ip address changes for whatever reason.

I have mine set to 60min or so as if I'm not around or awake I don't care if it takes upto 30min to renew and if I am around and I lose connectively the first thing I would do it log into the router to check what's going on.

It's normal for DHCP to be renewed at "half time" into the lease.

mentalinc

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#287086 5-Jan-2010 08:07

Cool thanks.

locky time.

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muppet

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#287239 5-Jan-2010 18:47

Is there a way on the RTA to lengthen the DHCP time? If so, I haven't found it in the GUI?

I'm using the PPP Passthru or whatever it's called, it's "half-bridge" mode.

The reason is my 5GT fills up with logs every time it gets a new DHCP lease (it's a firewall so it's not expecting this to happen even 5 minutes!)

It's not a big deal, but I'd love to set it for an hour or so.

Audiophiles are such twits! They buy such pointless stuff: Gold plated cables, $2000 power cords. Idiots.

OOOHHHH HYPERFIBRE!

Ragnor

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#287419 6-Jan-2010 13:05

I think it's under something like:

Advanced Config > Local network > DHCP Server Config > Lease Time

muppet

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#287429 6-Jan-2010 13:35

Yea, there's DHCP settings there, but they're only if the box is truely acting as a DHCP server for clients.

Currently the options there are set for a Lease Time of 1 day.

I've pretty much looked at the whole GUI and can't find anything, I was hoping it might be some tricky tweak in the CLI. But I've been through that (bare bones!) interface as well and given up, it's all a bit undocumented.

Thanks for your suggestion though.

HP

Shop now for HP laptops and other devices (affiliate link).

Ragnor

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#287455 6-Jan-2010 14:27

When in half bridge the RTA gives the WAN IP address to the WRT via DHCP so should be affected by that setting.

Tried going through the quick setup wizard, you might be able to change it that way the UI is a bit quirky.

mentalinc

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#289582 13-Jan-2010 11:34

as a heads up if you are running tomato version 1.24 or newer if it disconnects then reconnects every 30 seconds the following link will solve the problem.

http://www.genmay.com/showthread.php?t=822727

basically the following is the command to add were 192.168.0.1 is the adsl router.
iptables -I INPUT -p UDP -i vlan1 --dport 68 --sport 67 --source 192.168.0.1 -j ACCEPT

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Ragnor

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#289679 13-Jan-2010 15:32

FYI:

I think that DHCP renewing problem is fixed in a newer version of busybox (a component used in the Tomato build), should be fixed in 1.28 of the mainline Tomato but is fixed in various mods like Teddy Bears 1.27 ND USB version of the firmware.