Netgear R7000 behind Bell router, sporadic 2m disconnection

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Tectonic Plates
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Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Sun Apr 17, 2022 18:59    Post subject: Netgear R7000 behind Bell router, sporadic 2m disconnection Reply with quote
Hi,

Netgear R7000 working Ok, firmware 04-17-2021-r46380, connected to a dumb modem which has no built-in router.

until I made 2 changes.

1) Flashed 03-23-2022-r48567

2) Change internet provider, which is Bell Canada Fiber50 using a modem router HomeHub 2000 Model: Fast 5250. This modem has a built-in router and WiFi. I have disabled WiFi.

I connect the Netgear R7000 (subnet 192.168.1.0/24) on one of the LAN port of the Bell modem/router (subnet 192.168.2.0/24). As a result, there are now 2 routers chained together. Not sure if there is any adverse effects but it works.

THE PROBLEM: there are sporadic disconnections, about 2 or 3 times a day. Each time this lasts for about 2 minutes.

Additional info: When upgrading to 03-23-2022-r48567, I had enabled a few advanced functions. DNScrypt using Cisco OpenDNS as provider. And also a startup script using DNSmasq, updating the hosts to kill the ads. I suspected these advanced functions could be the cause and had disabled both. But this didn't fix the sporadic 2 minutes disconnection.


I contacted Bell tech support, one of the suggested workaround was to connect my network switch directly to the Bell router. Which means no longer using the Netgear R7000 router.

I tried that and indeed, the problem had disappeared. I would like to understand why but the Bell technicians could not give any clues. Can you please help me to troubleshoot further? Because I would prefer to manage my network via the Netgear router.


QUESTION 1: Is there any adverse effects when two routers are chained together?

QUESTION 2: Could the sporadic 2 minutes disconnection be a possible DD-WRT firmware issue?


Thanks in advance for any help

SOLVED: The cause was simply a scheduled reboot which was set to every 25920 seconds (7.2 days) which I forgot to disable.


Last edited by Tectonic Plates on Sun May 15, 2022 21:15; edited 2 times in total
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Tectonic Plates
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Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Sun Apr 17, 2022 19:03    Post subject: Reply with quote
Here is the script I was using to kill the ads. Inspired from this blog Ad Blocking with ddwrt
Not sure if this has left any remnant traces which could contribute to the disconnection issue.

Code:

curl -sS https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts | grep -E "^0.0.0.0" > /tmp/adblock-list
killall -HUP dnsmasq
stopservice dnsmasq && startservice dnsmasq
# generated filename ends by '?' b/c of CRLF added by Firefox
if [[ -f /tmp/adblock-list? ]]; then mv /tmp/adblock-list? /tmp/adblock-list; fi
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Mon Apr 18, 2022 7:32    Post subject: Reply with quote
My advice upgrade to the latest build and after upgrade reset to defaults.

After reset do only minimal setup e.g. username , password, Wireless setup with WPA2-PSK AES-128 and then see if you have any problems

A router behind a router should not be a problem

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
Tectonic Plates
DD-WRT User


Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Mon Apr 18, 2022 14:07    Post subject: Reply with quote
egc wrote:
My advice upgrade to the latest build and after upgrade reset to defaults.

After reset do only minimal setup e.g. username , password, Wireless setup with WPA2-PSK AES-128 and then see if you have any problems

A router behind a router should not be a problem


It's a relief to know that it's OK to have 2 routers chained together.

Thanks very much for the advice. It is going to take a few days to verify the fix. Because I need to watch the network almost the whole day to make sure there is no micro disconnection.
Tectonic Plates
DD-WRT User


Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Sun May 01, 2022 23:28    Post subject: Reply with quote
Quote:
A router behind a router should not be a problem


Unfortunately, it seems there is a problem. I have removed the Netgear router. Then connected the switch to the Bell modem/router. For 2 weeks, all devices works impeccably. Then I updated The Netgear R7000 to latest firmware 04-26-2022-r48741. All settings are minimum, pretty much the same as always which had always works for years before I swithched to Bell.

Then the sporadic Internet disconnection came back (2 minutes disconnection about 2 or 3 times a day).

I suppose it's a consequence of Double NAT. But I can't figure out where is the problem.

My Netgear R7000 WAN port is connected to a LAN port of a Bell modem/router. Both routers have DHCP but have different subnet.

Both routers have port-forwarding and UPnP disabled.

Among the possible solutions to eliminate Double NAT. One which could apply in my case is to place my Netgear WAN IP address in the DMZ of the Bell modem/router.

I set the Netgear WAN Static IP to be an address in the Bell modem subnet, but outside of its DHCP range. Just to make sure the Netgear WAN IP addr remains constant. Then add the Netgear WAN Static IP in the DMZ of the Bell router

Not sure how DMZ works, but when I connect a client to the Netgear router, which obtains an IP address from the Netgear subnet. The client can use the Intenet OK. But when I test traceroute 8.8.8.8, the 2 first hops is the IP addr of the Netgear followed by the IP addr of the Bell router.

So far I can't say if the DMZ approach is the fix to my issue (ie the rare & sporadic internet disconnection). Need to wait a few days to catch the event.

This post update is mainly to inform you that a router behind a router does bring a Double NAT issue. Which in my case translates into the mysterious sporadic Internet disconnection.
Alozaros
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Joined: 16 Nov 2015
Posts: 6410
Location: UK, London, just across the river..

PostPosted: Mon May 02, 2022 9:22    Post subject: Reply with quote
as my R7000 is in the same scenario(double NAT), and works just fine...
there are 3 options that come into my mind...
-bad power supply(if PSU cannot deliver the needed 3.5Amps)
-bad WAN port (try to put router in WAP mode and see what happens, in WAP mode you connect to the router switch(LAN) ports instead of using the WAN...
-bad DHCP client to client compatibility...i ve seen some clients or other 3rd party software routers to be bad with auto DHCP...so try to give it a static IP if this helps...(i guess you already did)

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TP-Link WR740Nv1 ---DD-WRT 55179 WAP
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TP-Link WR1043NDv2 -Gargoyle OS 1.15.x AP,DNS,QoS,Quotas
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Netgear XR500 --DD-WRT 55460 Gateway/DoH,Forced DNS,AP Isolation,4VLAN,Ad-Block,Firewall,Vanilla
Netgear R7800 --DD-WRT 55460 Gateway/DoT,AD-Block,Forced DNS,AP&Net Isolation,x3VLAN,Firewall,Vanilla
Netgear R9000 --DD-WRT 55363 Gateway/DoT,AD-Block,AP Isolation,Firewall,Forced DNS,x2VLAN,Vanilla
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Netgear R7000 --DD-WRT 55460 Gateway/SmartDNS/DoH,AD-Block,Firewall,Forced DNS,x3VLAN,VPN
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egc
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Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Mon May 02, 2022 10:18    Post subject: Reply with quote
I have an R6400v2 doing double NAT without a problem just as many more users.

Double NAT is not the problem, but what is your problem is hard to tell.

Usually resetting to defaults and changing Local IP address (if necessary) is sufficient.

Only problem I have seen (other then the ones described by @Alozaros) is with a very short lease time, so check that your Bell router has a lease time of 2 hours or more (120m) but usually I take one day 1440m, or even infinite.

Oh and placing the router in DMZ still double NATs

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
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Tectonic Plates
DD-WRT User


Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Mon May 02, 2022 16:00    Post subject: Reply with quote
Alozaros wrote:

-bad DHCP client to client compatibility...i ve seen some clients or other 3rd party software routers to be bad with auto DHCP...so try to give it a static IP if this helps...(i guess you already did)


This is it! And actually I could only understand the full meaning after reading this reddit post: HH3000 Advanced DMZ - Solution quote here the explanation for convenience

Quote:
the firewall of the client router is causing this issue. My router's firewall is setup to respond to pings from LAN, but to not respond to pings from WAN. The router, being connected to the HH3000 through its WAN port, cannot renew its DHCP lease


Indeed the Bell router has a 3 hours DHCP lease. I suppose the micro internet disconnections I experienced occurred every 3h but I am not actively using the Internet on those moments so I didn't see those events.

Based on the understanding I got on this reddit post. I changed the Netgear R7000 WAN Connection Type from "Automatic DHCP" to a Static IP address belonging to the Bell router subnet. And I made sure that IP address is outside of the DHCP range of the Bell router (192.168.2.10 to 254). Then I rebooted both routers. So far I cannot say if this is a real fix. But I didn't see yet any Internet disconnection.

Better still, that same reddit post has a better solution which is to use PPPoE passthrough. Which means I just need to change the Netgear WAN Connection Type to PPPoE. Connect the WAN port of the Netgear to a LAN port on the Bell modem/router. And that's it. No special config needed on the Bell router which could even be reset to its default factory setting.

I'll experiment this PPPoE passthrough solution and report back here about the outcome.
Tectonic Plates
DD-WRT User


Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Mon May 02, 2022 16:12    Post subject: Reply with quote
egc wrote:

Double NAT is not the problem, but what is your problem is hard to tell.

Usually resetting to defaults and changing Local IP address (if necessary) is sufficient.

Only problem I have seen (other then the ones described by @Alozaros) is with a very short lease time, so check that your Bell router has a lease time of 2 hours or more (120m) but usually I take one day 1440m, or even infinite.

Oh and placing the router in DMZ still double NATs


Confirmed everything you said. In particular Double NAT is NOT the problem. Maybe a bit of a few millisecs latency by the 2nd NAT overhead. But my use case is very basic which doesn't need any performance.

The real explanation is in my post just above. Which I hope is the correct diagnostic.


Quote:
Oh and placing the router in DMZ still double NATs


Confirmed as well! I was quite puzzled when doing `traceroute 8.8.8.8` I still see the two first hops are the two private IPs of both routers. I can't make sense of this, because I thought that when the Netgear IP lands in the DMZ of the Bell router, it would be exposed directly to the Internet without going through the Bell router.
kernel-panic69
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Joined: 08 May 2018
Posts: 14125
Location: Texas, USA

PostPosted: Mon May 02, 2022 20:27    Post subject: Reply with quote
Tectonic Plates wrote:
Here is the script I was using to kill the ads. Inspired from this blog Ad Blocking with ddwrt
Not sure if this has left any remnant traces which could contribute to the disconnection issue.

Code:

curl -sS https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts | grep -E "^0.0.0.0" > /tmp/adblock-list
killall -HUP dnsmasq
stopservice dnsmasq && startservice dnsmasq
# generated filename ends by '?' b/c of CRLF added by Firefox
if [[ -f /tmp/adblock-list? ]]; then mv /tmp/adblock-list? /tmp/adblock-list; fi

That killall -HUP dnsmasq line looks like a carryover from Adblock for DD-WRT (version 2). Which is then followed by a stopservice and startservice. This doesn't quite make sense to me because you're basically doing the same thing twice. Not sure which of the two is the cleaner option with current builds... @egc: your thoughts?

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egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Tue May 03, 2022 7:09    Post subject: Reply with quote
@kp69 that is indeed redundant.

stopservice/startserivce is the better option, in this case it does not matter but sometimes more than one service/process has to be stopped/started and the stopservice/startservice takes care of this

Example: "startservice mdns" will start avahi and dbus

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
Tectonic Plates
DD-WRT User


Joined: 02 Oct 2012
Posts: 65
Location: Canada

PostPosted: Sun May 15, 2022 21:11    Post subject: Reply with quote
egc wrote:
My advice upgrade to the latest build and after upgrade reset to defaults.

After reset do only minimal setup e.g. username , password, Wireless setup with WPA2-PSK AES-128 and then see if you have any problems

A router behind a router should not be a problem


Dear egc,

This is EXACTLY the solution! I should listen to your advice, although this would not explain the exact cause.

The cause of the reboot was a scheduled reboot, I set to every 30 days. But somehow the duration became 25920 seconds (7.2 hours). Maybe this is a bug in DDWRT firmware. When I disable the Adblock, I forgot about this scheduled reboot.
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