Asuswrt-Merlin 386.1_2 on RT-AC86U loses ISP connection (Xfinity/Comcast) in strange ways

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intelligo

New Around Here
I've noticed recent threads (below) describing problems similar to my own, where my Asus router spontaneously loses connection to the internet.



The threads have been so helpful that I am posting my experience for consideration. A few days after upgrading to 386.1_2 on my RT-AC86U, our home experienced a spontaneous internet outage. Thinking this was a routine hiccup, I power-cycled my router and cable modem (Arris SB6141), but, after a couple of attempts, there was no improvement. The status lights on my modem and router all indicated normal function. I then checked Xfinity's outage map and found that there was no widespread outage, so I then asked Xfinity to send a reset signal to my modem, which was still visible on the cable network. After a couple of attempts, there was no improvement. So, I settled down for some troubleshooting and connected a laptop by wire directly to the router and then the modem, which still indicated normal function. The laptop could not access the internet from the modem or the router, but strangely I could ping normally from both devices. I could also see that my router had a WAN IP address. The router and modem appeared to both be functioning normally, except none of my devices could reach the internet. I called Xfinity support, and they advised me to replace my modem, so I bought an Arris SB6190. After installing and provisioning the SB6190, I was able to access the internet when directly connected to the modem, but not via the router. I then did a full factory reset of the RT-AC86U and rebuilt my router configuration from scratch, including AiMesh. Internet was restored and all seemed to be functioning normally, but then a week later our home experienced the same type of outage. This time, I could still access the internet when directly connected to the modem. I could not, however, connect to the internet from my RT-RC86U, but, strangely, I could run speed tests and ping as if everything were normal. I didn't have time for a full repair, so I did a factory reset and set up a basic configuration without AiMesh until the weekend, when I plan to revert back to 384.19, which had been rock-solid.

Like others on this site have suspected, I agree that something is awry with 386.1_2, but I'm hardly qualified to speculate what the problem might be.;)
 

StR

Regular Contributor
FWIW, I had very similar "outage" situations with RT-N66R running Merlin fw v.380.70 happening over a long period of time, - almost every time when there was a massive download (e.g. some huge torrent file with a massive number of peers or several of large torrents at once - thus resulting in a large number of total concurrent connections), often after a few tens of minutes (10-20-30) from the start. There were no indications of the problem in the logs on the modem or the router. If left alone, usually the connectivity was restoring itself in some 10-20 minutes.
This is with Suddenlink. And I've read about other people with Suddenlink (or possibly also from some other cable ISPs) having some similar problems.

There were two hypothesis about what could be the culprit:
1. Some anti-DOS (denial-of-service attack) provision on the ISP side.
2. The router (NAT) was not keeping up with a high number of high-bandwidth simultaneous connections.
While I was unable to discern between the two with 100% certainty, lowering the maximum number of the simultaneous torrent connections seemed to have helped to almost eliminate those outages.

I have not seen those after upgrading my router to RT-AC86U with Merlin 386.0, so, after a few months from the upgrade, I bumped up the max number of connections, - and it has been working just fine. It was only yesterday that I updated the firmware to 386.1_2. So, I didn't have a chance to test that under a load.
 

jackc88

Occasional Visitor
@intelligo : I would check to make sure your modem is provisioned properly. I have had some very strange provisioning issues that xfinity hasn't offered any info on. As an alternative, you may want to look into the MAC clone feature on your router and use your laptop's MAC addr to test if that continues to work properly after taking your working laptop off the "WAN" side. As a side note, you might have some success reaching http://192.168.100.1 on your modem and view upstream/downstream stability and quality. Apologies, I am just glancing through your post. Let me know if you need further help.
FYI, I have experienced connectivity issues while a public IP was bound to the WAN interface. A "service restart_wan" would sometimes clear up the issue. In my particular case, it was related to xfinity's DHCP release/renew issues and udhcpc. The temporary workaround was to remove the defined "script" from running. I have since been running dhclient in a similar fashion and router changed from experiencing connectivity issues all day long to over 15 days and counting of uptime.

@StR : Were you experiencing "outage" did it only affect your torrent sessions or all Internet connectivity off your router? I haven't experienced those issues except off equipment from a couple of decades ago when memory was much more scarce. You could perhaps look at running "conntrack -C" when the issues occurs to see if you are close to the router's limit. If so, you may want to consider closing half-opened connections more aggressively starting with the IP stack running your torrent app. However, your first theory of the two seems more plausible. I have throttled or sent bittorent traffic into limbo on corporate edge routers.
 

KevTech

Very Senior Member
so I bought an Arris SB6190

Bad Choice:

As far as connecting straight to modem then changing to router and not having a connection.
Are you rebooting the modem when changing your connection?
Comcast allows only one MAC attached to the modem and that is the first MAC the modem sees during sync.
So when changing from straight to PC to another device connected to the modem you must reboot the modem so it releases the current attached MAC and attaches to the new MAC.
 

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