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#2677 - 06/09/15 01:32 AM Modem troubleshooting
gjj Offline

Registered: 12/08/14
Posts: 7
Hi all, I use MultiPing on a PC wired directly to the LAN port of our Comcast SMC Business Gateway. I ping,, and one internal LAN ip at 1 sec intervals.
Pretty much everyday the 3 internet addresses go to 100% packet loss. The internal IP is fine. Only powercycling the modem clears it up.

My question is this:
While I am down and Multiping is showing 100% PL, from any PC on the network, including the one that bypasses my switches and is cabled direct to a LAN port on the modem, I can ping the modem, LAN functionality is fine. I can log into the modems GUI and access the diagnostic screen from there I CAN ping internet addresses just fine.
I can ping all the addresses that the Multiping on the PC is showing 100% packet loss for.

Any ideas what could be going on here?
Hope I am explaining this clearly.

Thanks a million!

#2678 - 06/09/15 02:04 PM Re: Modem troubleshooting [Re: gjj]
Gary Offline
PingPlotter Staff

Registered: 10/30/13
Posts: 185
Hey Glen,

It sounds like the culprit here *may* be a NAT issue with your modem (where it's having a problem with the number of pings being sent).

If you're sending over 250,000 pings a day (3 targets @ 1 second each = 259,200), the NAT router has to store each of those so that it can route each one back to the right computer. If the manufacturer didn't test the modem to this scale - it *may* be holding on to that information until the state table gets full (at which point it would get confused, and wouldn't be able to figure out how to forward any additional pings).

There are a few things you can do to try and resolve this. The first option would be to check and see if there's a firmware update available for your modem. If everything *is* up to date on the firmware front, then you may want to check into your modem to see if there are any options to configure ICMP settings (to account for the number of pings being sent out).

If neither of the above two options seem to get things working as expected, you could possibly look into manually clearing out the state table on the modem (which would prevent you from having to power cycle it to get things working).

Hopefully this helps out! If you should find yourself with any questions, or needing any other assistance - please let us know.

Best wishes,


#2716 - 07/16/15 08:26 PM Re: Modem troubleshooting [Re: Gary]
gjj Offline

Registered: 12/08/14
Posts: 7
Thanks, could I cut down the number of targets and / or set MultiPing to ping say every 5 - 10 seconds?

New hitch - I put a router in and set it to use one of our other static IP's (we have 5 provided by comcast) to see if taking the routing off to modem helps.
It has been up all day.
I have MP pinging and as well as (
From 2:00 pm till 5:00 pm, the first two targets are showing 100% PL but the third (yours) is just fine and the Internet has been just fine.
Very peculiar.
Thanks in advance.....Glen

#2717 - 07/16/15 10:17 PM Re: Modem troubleshooting [Re: gjj]
Pete Ness Offline

Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
It's hard to know if cutting down the number of targets or frequency will impact anything. We've seen all sorts of crazy issues with router firmware - many things you'd never expect or foresee. Any settings change is certainly worth trying to see if you can isolate.

Probably Google is down, right? (Just kidding!). Removing NAT is a good thing to try. We have many customers using Comcast modems without problems, so I can't say for sure what's up here. You could always try PingPlotter to see which hop the problem starts at. Seems weird that one target works great and 2 don't (especially with something as robust as a Google DNS server).

Sorry I don't have more wisdom to add here. We'd be interested in hearing updates as you discover wrinkles / variables.

- Pete



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