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Connectivity and managing Your Comcast Business network
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benrady
New Member

Multi-second latency spikes to Comcast gateway for the last two days

I've had Comcast business class for just over a month now (installed on March 5th), and up until now it's been working perfectly. I've been very happy the performance of the connection. However, since yesterday, I've been seeing spikes of packet loss and latency (up to 10 seconds).

 

I can see this latency by just pinging the gateway assigned to me via DHCP (98.212.40.1). I've confirmed this from multiple sources, including the router that is directly connected to the cable modem. See the terminal session below for an example.

 

Restarting my cable modem (Motorola SB6121) and router (Linksys WRT54g) does not help. I don't believe the router to be at fault. I've attached a screenshot of my cable modem signal stats during one of these periods.

 

This is impacting my work. Any help or suggestions for troubleshooting this would be much appreciated.

 

SB6121 CableModem Signal

 

$ ping 98.212.40.1
PING 98.212.40.1 (98.212.40.1) 56(84) bytes of data.
64 bytes from 98.212.40.1: icmp_req=1 ttl=254 time=20.8 ms
64 bytes from 98.212.40.1: icmp_req=2 ttl=254 time=9.72 ms
64 bytes from 98.212.40.1: icmp_req=3 ttl=254 time=10.3 ms
64 bytes from 98.212.40.1: icmp_req=4 ttl=254 time=11.0 ms
64 bytes from 98.212.40.1: icmp_req=5 ttl=254 time=12.6 ms
64 bytes from 98.212.40.1: icmp_req=6 ttl=254 time=11.5 ms
64 bytes from 98.212.40.1: icmp_req=7 ttl=254 time=25.8 ms
64 bytes from 98.212.40.1: icmp_req=8 ttl=254 time=9.67 ms
64 bytes from 98.212.40.1: icmp_req=9 ttl=254 time=10.7 ms
64 bytes from 98.212.40.1: icmp_req=10 ttl=254 time=10.2 ms
64 bytes from 98.212.40.1: icmp_req=11 ttl=254 time=26.2 ms
64 bytes from 98.212.40.1: icmp_req=12 ttl=254 time=9.25 ms
64 bytes from 98.212.40.1: icmp_req=13 ttl=254 time=35.0 ms
64 bytes from 98.212.40.1: icmp_req=14 ttl=254 time=9.41 ms
64 bytes from 98.212.40.1: icmp_req=15 ttl=254 time=10.6 ms
64 bytes from 98.212.40.1: icmp_req=16 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=17 ttl=254 time=10.5 ms
64 bytes from 98.212.40.1: icmp_req=18 ttl=254 time=12.4 ms
64 bytes from 98.212.40.1: icmp_req=19 ttl=254 time=10.7 ms
64 bytes from 98.212.40.1: icmp_req=20 ttl=254 time=11.7 ms
64 bytes from 98.212.40.1: icmp_req=21 ttl=254 time=9.71 ms
64 bytes from 98.212.40.1: icmp_req=22 ttl=254 time=11.6 ms
64 bytes from 98.212.40.1: icmp_req=23 ttl=254 time=13.1 ms
64 bytes from 98.212.40.1: icmp_req=24 ttl=254 time=12.3 ms
64 bytes from 98.212.40.1: icmp_req=25 ttl=254 time=20.6 ms
64 bytes from 98.212.40.1: icmp_req=26 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=27 ttl=254 time=9.80 ms
64 bytes from 98.212.40.1: icmp_req=28 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=29 ttl=254 time=11.0 ms
64 bytes from 98.212.40.1: icmp_req=30 ttl=254 time=8.89 ms
64 bytes from 98.212.40.1: icmp_req=31 ttl=254 time=10.8 ms
64 bytes from 98.212.40.1: icmp_req=32 ttl=254 time=10.2 ms
64 bytes from 98.212.40.1: icmp_req=33 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=34 ttl=254 time=10.3 ms
64 bytes from 98.212.40.1: icmp_req=35 ttl=254 time=11.3 ms
64 bytes from 98.212.40.1: icmp_req=36 ttl=254 time=10.1 ms
64 bytes from 98.212.40.1: icmp_req=37 ttl=254 time=9.48 ms
64 bytes from 98.212.40.1: icmp_req=38 ttl=254 time=10.2 ms
64 bytes from 98.212.40.1: icmp_req=39 ttl=254 time=12.1 ms
64 bytes from 98.212.40.1: icmp_req=40 ttl=254 time=29.1 ms
64 bytes from 98.212.40.1: icmp_req=41 ttl=254 time=10.2 ms
64 bytes from 98.212.40.1: icmp_req=42 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=43 ttl=254 time=10.9 ms
64 bytes from 98.212.40.1: icmp_req=44 ttl=254 time=9.27 ms
64 bytes from 98.212.40.1: icmp_req=46 ttl=254 time=8010 ms
64 bytes from 98.212.40.1: icmp_req=49 ttl=254 time=5011 ms
64 bytes from 98.212.40.1: icmp_req=50 ttl=254 time=4012 ms
64 bytes from 98.212.40.1: icmp_req=51 ttl=254 time=3012 ms
64 bytes from 98.212.40.1: icmp_req=52 ttl=254 time=2012 ms
64 bytes from 98.212.40.1: icmp_req=53 ttl=254 time=4970 ms
64 bytes from 98.212.40.1: icmp_req=54 ttl=254 time=3971 ms
64 bytes from 98.212.40.1: icmp_req=55 ttl=254 time=2970 ms
64 bytes from 98.212.40.1: icmp_req=56 ttl=254 time=1962 ms
64 bytes from 98.212.40.1: icmp_req=57 ttl=254 time=962 ms
64 bytes from 98.212.40.1: icmp_req=58 ttl=254 time=12.6 ms
64 bytes from 98.212.40.1: icmp_req=59 ttl=254 time=9.81 ms
64 bytes from 98.212.40.1: icmp_req=60 ttl=254 time=11.4 ms
64 bytes from 98.212.40.1: icmp_req=61 ttl=254 time=13.2 ms
64 bytes from 98.212.40.1: icmp_req=62 ttl=254 time=10.7 ms
64 bytes from 98.212.40.1: icmp_req=63 ttl=254 time=10.5 ms
64 bytes from 98.212.40.1: icmp_req=64 ttl=254 time=10.4 ms
64 bytes from 98.212.40.1: icmp_req=65 ttl=254 time=9.37 ms
64 bytes from 98.212.40.1: icmp_req=66 ttl=254 time=9.84 ms
64 bytes from 98.212.40.1: icmp_req=67 ttl=254 time=10.3 ms
64 bytes from 98.212.40.1: icmp_req=68 ttl=254 time=6764 ms
64 bytes from 98.212.40.1: icmp_req=69 ttl=254 time=5761 ms
64 bytes from 98.212.40.1: icmp_req=70 ttl=254 time=4762 ms
64 bytes from 98.212.40.1: icmp_req=71 ttl=254 time=3762 ms
64 bytes from 98.212.40.1: icmp_req=72 ttl=254 time=2763 ms
64 bytes from 98.212.40.1: icmp_req=73 ttl=254 time=1763 ms
64 bytes from 98.212.40.1: icmp_req=74 ttl=254 time=763 ms
64 bytes from 98.212.40.1: icmp_req=75 ttl=254 time=25.8 ms
64 bytes from 98.212.40.1: icmp_req=76 ttl=254 time=10.6 ms
64 bytes from 98.212.40.1: icmp_req=77 ttl=254 time=9.88 ms
64 bytes from 98.212.40.1: icmp_req=78 ttl=254 time=10.0 ms
64 bytes from 98.212.40.1: icmp_req=79 ttl=254 time=10.6 ms
64 bytes from 98.212.40.1: icmp_req=80 ttl=254 time=11.2 ms
64 bytes from 98.212.40.1: icmp_req=81 ttl=254 time=11.5 ms
64 bytes from 98.212.40.1: icmp_req=82 ttl=254 time=10.1 ms
64 bytes from 98.212.40.1: icmp_req=83 ttl=254 time=11.1 ms
64 bytes from 98.212.40.1: icmp_req=84 ttl=254 time=10.8 ms
64 bytes from 98.212.40.1: icmp_req=85 ttl=254 time=11.2 ms
64 bytes from 98.212.40.1: icmp_req=86 ttl=254 time=9.50 ms
64 bytes from 98.212.40.1: icmp_req=87 ttl=254 time=10.1 ms
64 bytes from 98.212.40.1: icmp_req=92 ttl=254 time=1023 ms
64 bytes from 98.212.40.1: icmp_req=93 ttl=254 time=23.3 ms
64 bytes from 98.212.40.1: icmp_req=94 ttl=254 time=10.9 ms
64 bytes from 98.212.40.1: icmp_req=95 ttl=254 time=10.6 ms
64 bytes from 98.212.40.1: icmp_req=96 ttl=254 time=10.8 ms
64 bytes from 98.212.40.1: icmp_req=97 ttl=254 time=41.2 ms
64 bytes from 98.212.40.1: icmp_req=98 ttl=254 time=12.9 ms
^C
--- 98.212.40.1 ping statistics ---
98 packets transmitted, 91 received, 7% packet loss, time 97108ms
rtt min/avg/max/mdev = 8.892/716.428/8010.113/1670.875 ms, pipe 9
$ date
Mon Apr 7 23:00:04 CDT 2014

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5 REPLIES 5
Trusted Forum Contributor

Re: Multi-second latency spikes to Comcast gateway for the last two days

Your upstream power level is too high. It's supposed to be within 50, and with you being right on the border I bet that's causing an issue. Ask for a tech to come out and they should see that. If they don't mention it to them. They'll likely just place "insert technical term here" behind the modem which will downstep the modem signal a tad so it's within spec.

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benrady
New Member

Re: Multi-second latency spikes to Comcast gateway for the last two days

Upstream power level seems like a plasuable explanation. I checked it this morning and there were no latency spikes, and the power level was back down to 46-47. I'll monitor it and see if that correlation continues. 

 

If so, would a device like this amplifier solve the problem? I don't need to pay for a tech to install an inline amplifier.

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Trusted Forum Contributor

Re: Multi-second latency spikes to Comcast gateway for the last two days

It may, I don't have much experience with those so it's hard for me to say. In general if the upstream value is your problem, Comcast shouldn't charge you as it relates to something within your network.

 

You can sure call Comcast and ask what they say on it. If they see it above 50 they'll just send a tech as that's what they're trained to do. 

 

If they do charge you, though you should be able to stomp your feet a little and get it reversed. I've, unfortunately had to do it a few times for calls which were supposedly my fault.

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benrady
New Member

Re: Multi-second latency spikes to Comcast gateway for the last two days

I double checked the line running into my cable modem and found a splitter that was using the "tap" connection rather than "out". After checking online, it seems that can cause a degraded signal, and after changing it I haven't seen any problems.

 

Not sure why this started happening all of the sudden, however. I'm going to keep an eye on it and call up comcast for an amplifier if it happens again.

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dfasdsfdas
New Contributor

Re: Multi-second latency spikes to Comcast gateway for the last two days

hola...

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