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RT-AC68U DHCP issues

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Entropism

Occasional Visitor
Been trying to google my way out of this hole, but I can't find any definitive answer here:

I'm currently using an AC68U with an Arris CM8200, on a Comcast gigabit connection. This has been my setup for the past 2 months, since I moved to this house. Every few hours, my router basically craps the bed, loses all connection, and says "Your ISP's DHCP does not function properly", and I have to reboot my modem and router constantly before it regains connection. This happens 2-10 times per day.

I've found a few hits on similar issues online, but nothing really comes close to helping to fix the issue. I bought the 68U to replace a Netgear R6700v2 (because it's slow as all hell and not customizable at all), but this is beyond annoying.

Comcast says it's not them, but they don't know their butt from their elbow. Asus says it's Comcast, but they have about the same level of knowledge.

The sad part is I went with the 68U because I had a T-Mobile version of the 68U on FIOS for a few years, and it was just perfect.

Anyone have any suggestions? Or barring that, any replacement suggestions?

Thanks in advance!
 
Entropism said:
Been trying to google my way out of this hole, but I can't find any definitive answer here:

I'm currently using an AC68U with an Arris CM8200, on a Comcast gigabit connection. This has been my setup for the past 2 months, since I moved to this house. Every few hours, my router basically craps the bed, loses all connection, and says "Your ISP's DHCP does not function properly", and I have to reboot my modem and router constantly before it regains connection. This happens 2-10 times per day.

I've found a few hits on similar issues online, but nothing really comes close to helping to fix the issue. I bought the 68U to replace a Netgear R6700v2 (because it's slow as all hell and not customizable at all), but this is beyond annoying.

Comcast says it's not them, but they don't know their butt from their elbow. Asus says it's Comcast, but they have about the same level of knowledge.

The sad part is I went with the 68U because I had a T-Mobile version of the 68U on FIOS for a few years, and it was just perfect.

Anyone have any suggestions? Or barring that, any replacement suggestions?

Thanks in advance!
Click to expand...

My first step would be to trust and debug the error message. It says your router's ISP/WAN connection/euipment is troubled, so check it out.

Inspect the incoming cabling to the modem and to the router. Make sure it is undamaged, not bent beyond a 3" radius to avoid crushing the dielectric, connectors are solid, no water getting in, run through a proper grounding block, etc. Replace old, shoddy coax that can't handled 1 Gbps service. Run the coax straight to the modem; avoid unnecessary splitters/db drops/amplification and un-terminated ends.

Browse to the modem (http://192.168.100.1) and review its logs for unusual errors/signs of trouble.

Also, consider updating router firmware, then performing a factory default reset, and then reconfigure from scratch.

And make sure the modem power supply and adapter are healthy... modem and router on a UPS helps rule out poor power.

OE
 
Last edited:
Have you tried to set DHCP query frequency to Normal?

WAN - Internet Connection - DHCP query frequency

Might be worth a try.
 
I have, it was one of the first things I tried. Worked for about an hour, then crapped the bed again. Tried stock + merlin firmware as well.
 
OzarkEdge said:
My first step would be to trust and debug the error message. It says your router's ISP/WAN connection/euipment is troubled, so check it out.
Click to expand...

If this wasn't a known issue, I would. This also doesn't happen on other routers I have available. I purchased this thing to replace a godawful R6700v2 though, and I'm annoyed I'm basically throwing away $120.

Inspect the incoming cabling to the modem and to the router. Make sure it is undamaged, not bent beyond a 3" radius to avoid crushing the dielectric, connectors are solid, no water getting in, run through a proper grounding block, etc. Replace old, shoddy coax that can't handled 1 Gbps service. Run the coax straight to the modem; avoid unnecessary splitters/db drops/amplification and un-terminated ends.
Click to expand...

Like I said, everything works fine with other equipment. Cables are new and in good condition. Coax is old, and here before I was, but again, works fine with other equipment.
Browse to the modem (http://192.168.100.1) and review its logs for unusual errors/signs of trouble.
Click to expand...

Couldn't even begin to decipher it. I'll gladly cut and paste it though for anyone to assist.
Also, consider updating router firmware, then performing a factory default reset, and then reconfigure from scratch.
Click to expand...
Was on the latest Asus firmware, then the latest Merlin, and back & forth a few times since. Factory reset it a few times already, probably 6?
And make sure the modem power supply and adapter are healthy... modem and router on a UPS helps rule out poor power.
Click to expand...

Brand new surge protector, brand new router, brand new router power supply. Like I said, the whole thing it about 2 months old.

Edit: Just realised this may be taken as a bit of a snippy response. Wasn't meant to be at all! Truly appreciate any and all help in this thread!
 
Last edited:
Here's my modem's event log:

[
Code: 
1-1-1970, 0:0:48    Notice(6)    "Honoring MDD; IP provisioning mode = IPv6"
1-1-1970, 0:0:43    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:36    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:46:9    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:47    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:38    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:44:42    Critical(3)    "Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:44:40    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:42    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:42    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:41    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:40    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:39    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:33    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:32    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:32    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:31    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:27    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:26    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:26    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:25    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:24    Critical(3)    "16 consecutive T3 timeouts while trying to range on upstream channel 0;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:24    Critical(3)    "Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:24    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:19    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:16    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:15    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:14    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:14    Critical(3)    "16 consecutive T3 timeouts while trying to range on upstream channel 1;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:14    Critical(3)    "Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 15:40:14    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:38    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 13:0:36    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:36    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:47    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:39    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:46:57    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:46:57    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:46:42    Critical(3)    "Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:46:41    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:46:40    Critical(3)    "Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:43:2    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:15:41    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 12:13:43    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 2:28:56    Critical(3)    "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:45    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:36    Critical(3)    "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 2:26:47    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 2:26:47    Critical(3)    "No Ranging Response received - T3 time-out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
4-22-2018, 2:26:33    Critical(3)    "Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=5c:e3:0e:73:68:b9;CMTS-MAC=00:01:5c:8e:36:66;CM-QOS=1.1;CM-VER=3.1;"
 
Entropism said:
Here's my modem's event log:
4-22-2018, 15:46:9
4-22-2018, 15:44:42
4-22-2018, 13:0:36
4-22-2018, 12:46:57
4-22-2018, 2:26:47
Click to expand...

When the modem reboots, the log date resets to 1970, so the above times show your modem rebooting 5 times since early morning. I assume you have been rebooting your modem.

Ethernet cable from router to modem should be Cat 5e minimum.

Must be something odd on the WAN side of that router...

OE
 
Yeah, I've been unplugging the modem all day, every time the router goes out. I basically unplug both, let the router boot up fully, then plug the modem in.

All cables are brand new Cat 5Es. Ready to try to see if I can get a refund from Amazon at this point, and I'll just pick up a used R7800 or something. I was looking at Trendnet and TP Link, but I've heard about reliability issues with them.
 
Entropism said:
If this wasn't a known issue, I would. This also doesn't happen on other routers I have available. I purchased this thing to replace a godawful R6700v2 though, and I'm annoyed I'm basically throwing away $120.



Like I said, everything works fine with other equipment. Cables are new and in good condition. Coax is old, and here before I was, but again, works fine with other equipment.


Couldn't even begin to decipher it. I'll gladly cut and paste it though for anyone to assist.

Was on the latest Asus firmware, then the latest Merlin, and back & forth a few times since. Factory reset it a few times already, probably 6?


Brand new surge protector, brand new router, brand new router power supply. Like I said, the whole thing it about 2 months old.

Edit: Just realised this may be taken as a bit of a snippy response. Wasn't meant to be at all! Truly appreciate any and all help in this thread!
Click to expand...
Do you have the Cat 5e running through the surge protector? I did and I was having similar problems. I skipped the surge protector and ran it straight from my fiber router to my ac86u and that fixed my problem. Hope this helps.
 
Last edited:
T3 timeouts are normally noise on the upstream side.

Would help to see the signal levels of the modem.
 
Signal levels are within spec.

If this happens again do not turn off both router and modem so you can pinpoint which one is the issue.

Try rebooting just the router.
 
Most times a router reboot does nothing. I read one fix was to unplug both, let the router boot fully, then let the modem boot, and that fixes things temporarily. Been doing that since, seems to work.
 
Entropism said:
Most times a router reboot does nothing. I read one fix was to unplug both, let the router boot fully, then let the modem boot, and that fixes things temporarily. Been doing that since, seems to work.
Click to expand...
I saw a post were RMerlin suggested powering down the modem for 20-30 minutes. Have you powered it down that long or just a reboot? If you haven’t maybe try that?
 
I haven't, but I can try that now. I actually switched back to the Netgear R6700v2 temporarily until I (we) figure this out.
 
Seriously. We moved in 2.5 months ago, and had to switch from FIOS to Comcast. Haven't had an issue with Fios for 6 years, and Comcast/This equipment hasn't worked for more than 24 hours at a time. Very annoying.
 
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