ASUS RT-N16 drops every 5 mins on WAN DHCP lease time

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bbmak
DD-WRT User


Joined: 16 Jul 2007
Posts: 68

PostPosted: Thu Mar 31, 2011 1:49    Post subject: ASUS RT-N16 drops every 5 mins on WAN DHCP lease time Reply with quote
Hi,
Today, I switch my ISP to another company, and my WAN setting switches from PPPoE to Automatic Configuration - DHCP. Somehow the router gives me a lease time of 5 mins. Every 5 mins, my internet connection will drop. I call the ISP, and they told me that this should be a problem of the router. The 5 mins lease time is normal, and the connection won't drop. Does anybody experience this problem?

My WAN setting,
Automatic Configuration - DHCP
STP disable
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bbmak
DD-WRT User


Joined: 16 Jul 2007
Posts: 68

PostPosted: Thu Mar 31, 2011 2:17    Post subject: Reply with quote
Update on my issue:
I turn off SPI firewall. The problem is gone. Are there any built that fixes such problem?
jumran
DD-WRT User


Joined: 31 Jul 2009
Posts: 492
Location: Toronto, ON, CA

PostPosted: Thu Mar 31, 2011 3:32    Post subject: Reply with quote
Log in to the router and go to Administration>Commands Tab. Copy and paste the following code into the Command Shell text box. Press Save Firewall and reboot after a minute. This should resolve your issue.

Code:
wanf=`nvram get wan_iface`
iptables -I INPUT 2 -i $wanf -p udp --sport 67 --dport 68 -j ACCEPT

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Asus RT-N16 [Build King Kong 18050M NEWD-2 K2.6 + Optware + My Page] Mr. Green
bbmak
DD-WRT User


Joined: 16 Jul 2007
Posts: 68

PostPosted: Thu Mar 31, 2011 4:36    Post subject: Reply with quote
Thank you so much.
Do you know why this problem occur? Did Eko release any built that fixes such problem?
deltatux
DD-WRT User


Joined: 22 Jan 2011
Posts: 72

PostPosted: Thu Mar 31, 2011 6:17    Post subject: Reply with quote
Who's your ISP?

Also, it looks like it's allowing traffic from packets with a source port 67 to port 68... which is DHCP.

That means for some reason your firewall is blocking DHCP SYN/ACKs basically.

What build of DD-WRT are you running? I have build 16214 Mega and I leave it on automatic configuration for WAN and I definitely turn on my firewall.

I also have the RT-N16 router.

deltatux
jumran
DD-WRT User


Joined: 31 Jul 2009
Posts: 492
Location: Toronto, ON, CA

PostPosted: Thu Mar 31, 2011 13:18    Post subject: Reply with quote
This is known bug where the firewall blocks DHCP renewal requests on WAN causing disconnects on renewal. There is a bug ticket that was created a long time ago but was never fixed.


bbmak wrote:
Thank you so much.
Do you know why this problem occur? Did Eko release any built that fixes such problem?

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Asus RT-N16 [Build King Kong 18050M NEWD-2 K2.6 + Optware + My Page] Mr. Green
bbmak
DD-WRT User


Joined: 16 Jul 2007
Posts: 68

PostPosted: Thu Mar 31, 2011 13:59    Post subject: Reply with quote
deltatux wrote:
Who's your ISP?

Also, it looks like it's allowing traffic from packets with a source port 67 to port 68... which is DHCP.

That means for some reason your firewall is blocking DHCP SYN/ACKs basically.

What build of DD-WRT are you running? I have build 16214 Mega and I leave it on automatic configuration for WAN and I definitely turn on my firewall.

I also have the RT-N16 router.

deltatux


I am using Sonic.net. I call the support. The support said that 5 mins lease time is normal. It won't drop. The problem may be on your router.
Using Eko Mini built 3/10/2011
bbmak
DD-WRT User


Joined: 16 Jul 2007
Posts: 68

PostPosted: Thu Mar 31, 2011 14:01    Post subject: Reply with quote
jumran wrote:
This is known bug where the firewall blocks DHCP renewal requests on WAN causing disconnects on renewal. There is a bug ticket that was created a long time ago but was never fixed.


bbmak wrote:
Thank you so much.
Do you know why this problem occur? Did Eko release any built that fixes such problem?


icic... anyway, Thank you for your help.
deltatux
DD-WRT User


Joined: 22 Jan 2011
Posts: 72

PostPosted: Thu Mar 31, 2011 19:52    Post subject: Reply with quote
bbmak wrote:
deltatux wrote:
Who's your ISP?

Also, it looks like it's allowing traffic from packets with a source port 67 to port 68... which is DHCP.

That means for some reason your firewall is blocking DHCP SYN/ACKs basically.

What build of DD-WRT are you running? I have build 16214 Mega and I leave it on automatic configuration for WAN and I definitely turn on my firewall.

I also have the RT-N16 router.

deltatux


I am using Sonic.net. I call the support. The support said that 5 mins lease time is normal. It won't drop. The problem may be on your router.
Using Eko Mini built 3/10/2011


Try BrainSlayer's builds ...

deltatux
phuzi0n
DD-WRT Guru


Joined: 10 Oct 2006
Posts: 10143

PostPosted: Thu Mar 31, 2011 21:13    Post subject: Reply with quote
No there is not any build that fixes it so don't waste your time. The firewall scripts works fine. The problem is really with half-bridge modems that assign the router a public IP but send DHCP from their private LAN IP which is outside of the WAN subnet. The firewall prevents the lease from being renewed since the replies are coming from a different subnet than the WAN IP is in. After the lease expires, the WAN IP is lost, and the firewall no longer cares where the new DHCP lease comes from.

http://svn.dd-wrt.com/ticket/973

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gatorback
DD-WRT User


Joined: 04 Feb 2007
Posts: 352
Location: Fountain of Youth

PostPosted: Thu Mar 31, 2011 21:36    Post subject: DD-WRT v24-sp2 (11/21/10) big on ASUS RT-N16 Reply with quote
DD-WRT v24-sp2 (11/21/10) big (SVN revision 15778) connected to WAN via DHCP is working fine. IMHO a 5 minute lease time is unreasonably short within the context.
Venique
DD-WRT Novice


Joined: 09 Jun 2011
Posts: 6

PostPosted: Fri Jun 10, 2011 6:04    Post subject: Reply with quote
So I must turn off ISP firewall AND enter this code:
Code:
wanf=`nvram get wan_iface`
iptables -I INPUT 2 -i $wanf -p udp --sport 67 --dport 68 -j ACCEPT

or just enter this code without deactivating firewall will be enough?
And I must enter this command after every router reboot (from GUI or by unplugging power cable) or it will stay in it for ever?
jumran
DD-WRT User


Joined: 31 Jul 2009
Posts: 492
Location: Toronto, ON, CA

PostPosted: Fri Jun 10, 2011 6:27    Post subject: Reply with quote
Venique wrote:
So I must turn off ISP firewall AND enter this code:
Code:
wanf=`nvram get wan_iface`
iptables -I INPUT 2 -i $wanf -p udp --sport 67 --dport 68 -j ACCEPT

or just enter this code without deactivating firewall will be enough?
And I must enter this command after every router reboot (from GUI or by unplugging power cable) or it will stay in it for ever?


You do not need to change firewall settings. The following commands will simply instruct router firewall to allow DHCP renewals to go through and once you save the firewall rule by following the provided instructions, you should not need to do this again unless your reset your router to setting defaults or upgrade firmware. Log in to the router and go to Administration>Commands Tab. Copy and paste the following code into the Command Shell text box. Press Save Firewall and reboot after a minute. This should resolve your issue.

Code:
wanf=`nvram get wan_iface`
iptables -I INPUT 2 -i $wanf -p udp --sport 67 --dport 68 -j ACCEPT

_________________
Asus RT-N16 [Build King Kong 18050M NEWD-2 K2.6 + Optware + My Page] Mr. Green
Venique
DD-WRT Novice


Joined: 09 Jun 2011
Posts: 6

PostPosted: Fri Jun 10, 2011 12:02    Post subject: Reply with quote
I do that you said:
[img]http://img.leprosorium.com/1157266[/img]
Started online radio and EVE Online client, press "DHCP Release" - router droped DCHP, all is okay - radio playing and connection to the EVE-server is stable. But after I pressed "DHCP Renew" radio stops and EVE client crashes because connection to the server was lost.
Sad
jumran
DD-WRT User


Joined: 31 Jul 2009
Posts: 492
Location: Toronto, ON, CA

PostPosted: Fri Jun 10, 2011 15:49    Post subject: Reply with quote
Venique wrote:
I do that you said:
[img]http://img.leprosorium.com/1157266[/img]
Started online radio and EVE Online client, press "DHCP Release" - router droped DCHP, all is okay - radio playing and connection to the EVE-server is stable. But after I pressed "DHCP Renew" radio stops and EVE client crashes because connection to the server was lost.
Sad


Why are you releasing or renewing DHCP manually? DHCP will auto renew when lease expires.

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