Connectivity
Connectivity and managing Your Comcast Business network
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Visitor

Frequent short outages

For the past several days, I have been experiencing frequent, but short, outages. Usually about once an hour or so my connection will be completely unusable for anywhere from 20 seconds to a few minutes. During this time, no connection to the Internet is available (e.g. webpages don't load, streaming video stalls, games get disconnected, pings timeout, etc.). This is especially disruptive to file transfers over VPN.

 

None of the stats on my modem seem out-of-line (all of the readings for downstream power are between -9.1 and -6.2 dBmV and the readings for downstream snr are between 36.5 and 39.2 dBmV). Leading up to the outage, there is no sign that it's coming; for example, from a recent ping session, pings are all right around 35ms, and then suddenly silence:

 

% ping 8.8.8.8

PING 8.8.8.8 (8.8.8.8): 56 data bytes

64 bytes from 8.8.8.8: icmp_seq=0 ttl=46 time=33.732 ms

64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=35.332 ms

64 bytes from 8.8.8.8: icmp_seq=2 ttl=46 time=34.633 ms

64 bytes from 8.8.8.8: icmp_seq=3 ttl=46 time=34.145 ms

64 bytes from 8.8.8.8: icmp_seq=4 ttl=46 time=34.524 ms

64 bytes from 8.8.8.8: icmp_seq=5 ttl=46 time=34.464 ms

64 bytes from 8.8.8.8: icmp_seq=6 ttl=46 time=34.597 ms

64 bytes from 8.8.8.8: icmp_seq=7 ttl=46 time=42.734 ms

64 bytes from 8.8.8.8: icmp_seq=8 ttl=46 time=39.348 ms

64 bytes from 8.8.8.8: icmp_seq=9 ttl=46 time=33.830 ms

64 bytes from 8.8.8.8: icmp_seq=10 ttl=46 time=34.647 ms

64 bytes from 8.8.8.8: icmp_seq=11 ttl=46 time=34.115 ms

64 bytes from 8.8.8.8: icmp_seq=12 ttl=46 time=35.096 ms

64 bytes from 8.8.8.8: icmp_seq=13 ttl=46 time=33.829 ms

64 bytes from 8.8.8.8: icmp_seq=14 ttl=46 time=34.962 ms

64 bytes from 8.8.8.8: icmp_seq=15 ttl=46 time=33.659 ms

64 bytes from 8.8.8.8: icmp_seq=16 ttl=46 time=34.197 ms

64 bytes from 8.8.8.8: icmp_seq=17 ttl=46 time=34.023 ms

64 bytes from 8.8.8.8: icmp_seq=18 ttl=46 time=34.246 ms

64 bytes from 8.8.8.8: icmp_seq=19 ttl=46 time=35.128 ms

Request timeout for icmp_seq 20

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64 bytes from 8.8.8.8: icmp_seq=50 ttl=46 time=33.953 ms

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12 REPLIES 12
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Trusted Forum Contributor

Re: Frequent short outages

-10 is actually the cut off for downstream. So if one or more of your channel is sitting at -9.1 it's very likely it's fluctating out of spec and causing you issues. Did you pull those numbers while the issue was happening?

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Visitor

Re: Frequent short outages

Those numbers are from when the issue was happening. Only one of the bands (615 MHz) was at -9.1. Right now, that band is at -9.0.

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Trusted Forum Contributor

Re: Frequent short outages

have you tried removing your router, if you have one, and seeing if the problem persists?

I will say that I have been told by technicians that while -10dbmv is the cutoff for downstream power, your power should really not be below -7 for ideal performance. are there any splitters installed between the modem and the coax coming off the pole? if so, try removing them temporarily & check your readings
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Visitor

Re: Frequent short outages

Unfortunately, my modem *is* my router, so not much chance of removing the router Smiley Happy

 

I'll have to take a trip up into the attic to check if there are any splitters involved (there shouldn't be many, as I don't have Cable TV, so no need for any connections other than the modem)

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Trusted Forum Contributor

Re: Frequent short outages

As long as you are wired into that combo box you should be ok. 

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Visitor

Re: Frequent short outages

Additionally, I doubt the issue is between the modem and my computer, as I never have any trouble accessing the modem's configuration page (or anything else within my local network for that matter), it's only the connection to the outside world.

 

That said, I now have two things to try when I get home (i.e. eliminating any splitters on my line if there are any, and seeing if I can reproduce the issue with a computer plugged directly into the modem)

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Visitor

Re: Frequent short outages

Turns out there were still some splitters up there (that were serving zero purpose; it seems that the guy who installed my cable just left them connected to some several-metre long coax cables; *sigh*). After removing them, all of my downstream power readings are between -1.1 dBmV and -0.2 dBmV.

 

Thanks for your help.

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Trusted Forum Contributor

Re: Frequent short outages

that's quite a rise in levels!

 

hope it resolves your connectivity issues

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Visitor

Re: Frequent short outages

Unfortunately, this hasn't fixed the issue. Despite the now-excellent power levels, the connection still went out twice (that I know of) last night.

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Trusted Forum Contributor

Re: Frequent short outages

when the connection goes out, can you still ping your gateway? (eg, "ping 10.1.10.1")

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Re: Frequent short outages

Yes, I can. As well as any other hosts on the local network.

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Trusted Forum Contributor

Re: Frequent short outages

this is a weird one. Possibly try doing a traceroute during an outage to see if it's the modem dropping packets or if it's further along the path. The only thing i could think of would be either an intermittently failing modem or piece of pole equipment in your area. MAYBE a bad coax in your house/between it and the pole it connects to, but that would probably produce worse signals than you have.

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