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RAZ Black
join:2001-10-04
united state

RAZ Black

Member

[CBN] any thoughts on what is causing dropped packets at modem?

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This has been going on for a while for me, and I'm not so sure what is going on. Tech doesn't see any loss between the modem and them; however, I get this on a regular basis: (if I let the tracert continue on for hours, the total Loss count climbs into the hundreds).

This tracert is from a workstation connected directly to one of the ports on the modem, no internal equipment between. I've tried different ports on the back, no difference. I also seem the same results from my internal network, and from my firewall device.

Is it possible that their are issues with the Ethernet ports or some firmware problem with this device? (SMCD3GN2)

or could this be an TCP configuration issue with these devices, and I need to make some core changes to how TCP is working with it?

just a note: I know this kind of behavior can be seen with very high traffic usage, but I've been watching this now sit at less than 200Kbps for a while.
aguen
Premium Member
join:2003-07-16
Grants Pass, OR

aguen

Premium Member

Instead of using whatever that tool is, why not use this one provided by this site »Charter Spectrum Internet Line Monitoring - It's free
Please ensure that your router wan port responds to pings and if possible, bridge your modem so that your router gets the public IP address. Let the test run for a day or so, then if needed please reply back to this thread with a link to the trace.

B4Knight
Premium Member
join:2014-03-20
Colon, MI

B4Knight

Premium Member

Both the Line Monitoring tool here on the site and Ping Plotter are excellent tools for troubleshooting or analyzing your connection

»www.pingplotter.com/

RAZ Black
join:2001-10-04
united state

RAZ Black to aguen

Member

to aguen
it was something similar to pingplotter... i'll do the line monitoring and see how things look over the week.
RAZ Black

RAZ Black

Member

ok, I now have an explanation for this.

after a... month or so, working on this issue and doing a reverse trace (as suggested before) I nailed down the problem.

They have disabled/blocked ICMP on the modem, which is fine with me I suppose as I guess it prevents snoops... however, it has been disabled on both interfaces (internal and external). IMO.. it "should not disable it on the internal side".

so... ok, that just means I have to monitor the connection by checking with other sources... fine.
aguen
Premium Member
join:2003-07-16
Grants Pass, OR

aguen to RAZ Black

Premium Member

to RAZ Black
Did Charter provide your cable modem, or did you purchase it?
This device is way more than just a modem and is a full blown router with wireless and it's own firewall, etc.:

Preface
vi
SMCD3GN2 Wireless Cable Modem User Manual Key Features

The following list summarizes the Gateway’s key features.

Integrated, CableLabs-compliant DOCSIS 1.1/ 2.0 /3.0 cable modem
y
Four 10/100/1000 Mbps Auto-Sensing LAN ports with Auto-MDI/MDIX
y
High-speed 300 Mbps IEEE 802.11n Wireless Access Point
y
Dynamic Host Configuration Protocol (DHCP)
for dynamic IP configuration, and Domain
Name System (DNS) for domain name mapping
y
One USB 2.0 port
y
IEEE 802.11 b/g/n interoperability with multiple vendors
y
Wireless WEP, WPA, and WPA2 encryption, Hide SSID, and MAC Filtering
y
VPN pass-through support using PPTP, L2TP, or IPSec
y
Advanced SPI firewall Gateway for enhanced network security from attacks over the
Internet:
– Firewall protection with Stateful Packet Inspection
– Client privileges
– Hacker prevention
– Protection from denial of service (DoS) attacks.

– Network Address Translation (NAT)

Any of the above BOLDED items would be capable of causing the WAN port to ignore ICMP packets. There is an Owners Manual for this device which might help you but if you don't have sufficient access to this device then maybe Charter can help you.

RAZ Black
join:2001-10-04
united state

RAZ Black

Member

its' provided by Charter, so they have full access for configuration... even as a CBN customer, I have none (that I'm aware of) access to any possible configurations for it.... unfortunately.
aguen
Premium Member
join:2003-07-16
Grants Pass, OR

aguen to RAZ Black

Premium Member

to RAZ Black
If your "account" includes at least one static IP address, what nic has that address assigned to it?