MB7621 modem bottleneck and slow speeds

I know this issue has come up on the forum before, but I haven't seen a solution. I have 800 Mbps service, but am only getting 15 Mbps. I should be at least getting 300. I've had a Comcast tech out to the house and cabling is getting plenty of speed into the modem itself. He checked the speed coming out of the modem. Less than 100. He said the problem is the modem. Please, any help would be great!

Cable Specification Version DOCSIS 3.0

Hardware Version V1.0

Software Version 7621-5.7.1.10

CM Certificate Installed 5.7.1mp4

Log

Time	Priority	Description
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=****;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=**;CMTS-MAC=**;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6

Startup Sequence

Startup Step	Status	Comment
Acquire Downstream Channel	591000000 Hz	Locked
Upstream Connection	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+

Connection Status

System Up Time	0 days 05h:40m:03s
Network Access	Allowed

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	28	591.0	6.8	43.3	0	0
2	Locked	QAM256	21	549.0	6.1	42.5	0	0
3	Locked	QAM256	22	555.0	6.2	42.4	0	0
4	Locked	QAM256	23	561.0	6.3	42.7	0	0
5	Locked	QAM256	24	567.0	6.4	42.8	0	0
6	Locked	QAM256	25	573.0	6.5	42.9	0	0
7	Locked	QAM256	26	579.0	6.6	43.1	0	0
8	Locked	QAM256	27	585.0	6.7	43.1	0	0
9	Locked	QAM256	29	597.0	6.9	43.4	0	0
10	Locked	QAM256	30	603.0	6.9	43.4	0	0
11	Locked	QAM256	31	609.0	6.9	43.5	0	0
12	Locked	QAM256	32	615.0	7.0	43.5	0	0
13	Locked	QAM256	33	621.0	6.9	43.5	0	0
14	Locked	QAM256	34	627.0	7.0	43.7	0	0
15	Locked	QAM256	35	633.0	7.0	43.7	0	0
16	Locked	QAM256	36	639.0	7.2	43.4	0	0
17	Locked	QAM256	37	645.0	7.5	46.9	0	0
18	Locked	QAM256	38	651.0	7.6	47.0	0	0
19	Locked	QAM256	39	657.0	7.6	46.8	0	0
20	Locked	QAM256	40	663.0	7.7	47.0	0	0
21	Locked	QAM256	41	669.0	7.7	47.0	0	0
22	Locked	QAM256	42	675.0	7.9	47.2	0	0
23	Locked	QAM256	43	681.0	8.0	47.2	0	0
24	Locked	QAM256	44	687.0	8.1	46.9	0	0
Total							0	0

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	ATDMA	2	5120	22.8	39.8
2	Locked	ATDMA	1	5120	16.4	39.7
3	Locked	ATDMA	3	5120	29.2	39.2
4	Locked	ATDMA	4	5120	35.6	39.2
5	Not Locked	Unknown	0	0	0	0.0
6	Not Locked	Unknown	0	0	0	0.0
7	Not Locked	Unknown	0	0	0	0.0
8	Not Locked	Unknown	0	0	0	0.0

Responses

BruceW

Gold Problem Solver

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26.4K Messages

1 year ago

MB7621 modem ... 800 Mbps service, but am only getting 15 Mbps ... He said the problem is the modem ...

It's possible that the modem is bad, but low speeds are much more often due to problems with the connection between the modem and Comcast's network or, less often, problems further upstream. Some of the downstream power levels are just a bit high, but I would guess not high enough to cause such a large loss of speed. Otherwise SNR, error counts, and upstream power levels all look OK.

Please post the modem's event log (from http://192.168.100.1/MotoSnmpLog.asp). Be sure to remove or blot out any MAC addresses. Forum security processing considers them "personal information" and may prevent the event log from posting if these are present.

Copy and pasted text is preferred over images. Be aware that, if you post any images, your message will be made Private for a time, as all images must be approved by the Forum Moderators before the messages containing them become generally visible.

Please see Internet Troubleshooting Tips for additional information you may find helpful.

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(edited)

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U

user_qwjhte

5 Messages

1 year ago

Thank you! You can find the event log in the original post already. The speed coming in from Comcast is fast/normal according to the tech.

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U

user_qwjhte

5 Messages

1 year ago

Believe me I've tried ALL the troubleshooting tips :)

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BruceW

Gold Problem Solver

•

26.4K Messages

1 year ago

... You can find the event log in the original post already ...

Oops! Sorry, my bad. Can't really tell much from it. It looks like a startup sequence and those often throw an error or two.

If I had this problem and didn't have a spare modem handy, I'd probably try renting one of Comcast's gateway devices for a week or so to see how it compares with the MB7621. If the rental is OK you'd have to decide whether to continue using it, or purchasing a replacement for the MB7621. If the rental has the same problem then you'd need to have Comcast take another try at fixing the problem.

Please let us know what you decide and how this turns out. Good luck!

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

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user_qwjhte

5 Messages

1 year ago

I bought a new modem, Netgear CM1200 and the speeds I'm getting are now almost 400 mbps, so yes it's much better now! I guess the problem was the modem but I have no idea what was wrong. I'm wondering... my old modem's top speed was roughly 300-500 mbps and the speed I was getting (15) is a small percentage of that. My new modem's top speed is 1gig (my plan is 800), and 400 is a fraction of that. I'm wondering if I should be getting more? Granted, I am on WiFi, but I am sitting right by the router.

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user_qwjhte

5 Messages

1 year ago

Actually I think I spoke too soon. The internet kept going (completely) out yesterday after installing the modem. Orange internet light on the router. Modem lights were ok. I used the Xfinity app to troubleshoot. At one point it said there was a problem upstream, so they scheduled a tech to come out. I updated the firmware on the router (Archer AX50). No more orange light on the router, but now I'm getting speeds of ~30mbps and below consistently on my phone. My laptop sometimes pulls ~400 mbps but other times it's down to 30 mbps. Internet is now consistently on, but the speeds are varying a lot. I've done several modem/router reboots. Could it be my router?

I have a tech coming out soon, but I don't think they'll be able to do anything. It's not a consistent problem. There's nothing they can do if the internet coming into the modem is fine (which is what he said last time.)

So to recap, the tech said the internet looked good coming into the house. The problem was with the modem. I got a new modem. Now the problem is less bad, but still not great. I don't know what else to do except switch to AT&T. They have fiber in my area.

(edited)

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XfinityWilliam

Official Employee

•

1.2K Messages

Hello @user_qwjhte. Thanks for this conversation here on Forums. Before the technician comes out, we can take a closer look at your signal and see if we can find any issues and have you relay that to the technician.

Will you please send our team a direct message with your full name and full address?
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1 year ago

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BruceW

Gold Problem Solver

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26.4K Messages

1 year ago

... I don't know what else to do ...

Keep after them! Troubleshooting intermittents is always a bit of a pain, but Comcast is a 100 billion dollar corporation. They have essentially unlimited means to figure out things like this if "encouraged". The help XfinityWilliam has offered may smooth the road a bit.

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user_qwjhte

MB7621 modem bottleneck and slow speeds

BruceW

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

user_qwjhte

user_qwjhte

BruceW

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

user_qwjhte

user_qwjhte

XfinityWilliam

BruceW

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

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