[tech2016]

DD-WRT v3.0-r43266 std (05/27/20)
TP-Link C1900 router

My tp-link router was working fine with Comcast 75mbps connection. I recently upgraded to ATT fiber gigabit service and I've been having intermittent internet connection issues. Multiple laptops in the house loose internet connection at the same time and then get it back few seconds later and it happens 5 or 6 times a day. Not sure whether this is caused by tp-link router or AT&T modem. How can I diagnose this issue further.

[Wildlion]

Have you checked the resource usage on the router?

Do you have any QOS on?

One thing to note is that sometimes ISPs will give you a burst of bandwidth initially and then level you off. THe intent is to get you the content quickly so it feels faster to you as well as get you off the connection for others.

Have you tried a speed test to see what the router's max is?

ISP modems have diagnostic pages you can check for uptimes and errors.

[MichaelC]

I've had a similar problem with my C1900 and haven't found a solution yet:

https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=325083

[tech2016]

I'll check the cpu/memory usage next time it happens.

I enabled QoS and the problem still happened. I turned it off.

The ISP modem log shows messages like this-
192.168.2.63 23.199.248.27 TCP IP Source Address
23.199.250.75 70.252.19.41 TCP Generic Discards
192.168.10.65 17.253.3.209 TCP Invalid IP Packet
Most of the messages say 'Generic Discards' and some other messages. Not sure whether it indicates any issue with modem or these are expected normal messages.

I did speed test with fast.com on a desktop connected to router with ethernet and it showed download and upload speed of about 800mbps.

The speed test page on router itself showed internet speed of only 72Mbps which is strange.
I also did speed test using ISP modem and it showed 990mpbs.

[WouldRatherBeFOSS]

Compare perhaps this thread of mine.

[redhawk0]

Recently, I had similar issues on my R7000. Here are the settings that fixed it for me.

redhawk


Setup>>Setup

Shortcut Forwarding Engine - DISABLED

Use DNSMasq for DNS - Checked
DHCP-Authoritative - Checked
Recursive DNS Resolving (Unbound) - Checked
Forced DNS Redirection - Checked

Services>>Services

SmartDNS Resolver - Enable
Dualstack IP Selection -Disable
Prefetch Domain -Enable
Serve Expired -Enable