Can't ping or tracert

[rkl122]

Hello. I just noticed that my smtp connection to my server (smtp.comcast.net) is not sending mail. The same smtp client (Pegasus) receives mail ok. So I tried pinging and trace routing from an administrative command prompt, and notice I can't get a response from anywhere outside the home network. Everything times out. Same thing happens from second win 7 machine on the home network, but that one sends mail ok (different mail server). Both machines are hard wired to the cable modem (supplied by Comcast). I can send mail through the same smtp.comcast.net account from an iPad over WiFi, no problem. No browsing issues. I have reset the modem from both its browser interface and by unplugging/replugging. No improvement.

Would appreciate tips on how to diagnose this. Thank you.

Edit: the following does work without timing out on some tries, not all:
http://tools.pingdom.com/ping/?target=smtp.comcast.net&o=2&save=false

 

[LMiller7]

It is possible that your ISP is blocking ping and tracert. Check with them before proceeding further.

 

[rkl122]

Thanks for the response. Comcast says it is not blocking ping or tracert. They will not help with my email client, since - after ascertaining that my send mail settings are correct - it is beyond their responsibility, but when I mentioned that two different machines (one of which does not even have the same email client as I use) both hard wired to Comcast's cable modem, and both having normal internet access (as shown in the browser), he says it is very unusual that neither ping nor tracert work. Since the only thing these two machines have in common, he accepts that Comcast bears sufficient responsibility to have a next level expert call me back to look deeper.

From my own reading, the next step would be to clear out all or part of the ARP cache. There are a number of entries in there beginning with 224 and 236 and part of what "WhoIs" says about these is "Comment: Addresses starting with a number between 224 and 239 are used for IP
multicast. IP multicast is a technology for efficiently sending the same content to multiple
destinations. It is commonly used for distributing financial information and video streams,
among other things." Huh? How'd these entries get in my ARP?

Should I flush these? Can any harm come from flushing the ARP, either partially or completely? To show my level of naivete, despite reading, I'm still not understanding just what is the ARP.

Thx for any help. -Ron

 

[rkl122]

I've fixed my mail client problem (previous restore point), but our two desktops, both cabled to the same modem/router, are still getting timeouts on all internet pings (all four packet probes, for popular websites which are easily pinged from a friend's machine). I've tried various "fixes," including a ipconfig flush DNS and completely removing AVG. Nothing has helped so far. I've not tried flushing the ARP. My browsing activity is normal.

The network adapter subsection of TroubleShooting>Network and Internet in the control panel gives the following. Does anyone know how to interpret this? Or which section of the Event Viewer to use? Suggestions appreciated.

****************
The connection between your access point, router, or cable modem and the Internet is broken Detected

The network gateway is accessible, but Windows couldn’t receive network traffic from the Internet.
Your broadband modem is experiencing connectivity issues Completed
Restart your broadband modem: 1. Unplug or turn off the modem. 2. After all the lights on the modem are off, wait at least 10 seconds. 3. Turn the modem on or plug it back into the power outlet. To restart a modem that has a built-in battery, press and quickly release the Reset button. If this doesn't fix the problem, contact your Internet service provider.



Detection details

Diagnostics Information (Network Adapter)
Details about network adapter diagnosis: Network adapter Local Area Connection driver information: Description . . . . . . . . . . : Realtek RTL8168C(P)/8111C(P) Family PCI-E Gigabit Ethernet NIC (NDIS 6.20) Manufacturer . . . . . . . . . : Realtek Provider . . . . . . . . . . . : Microsoft Version . . . . . . . . . . . : 7.2.1127.2008 Inf File Name . . . . . . . . . : C:\Windows\INF\netrtx64.inf Inf File Date . . . . . . . . . : Monday, July 13, 2009 8:37:30 PM Section Name . . . . . . . . . : RTL8168C.ndi Hardware ID . . . . . . . . . . : pci\ven_10ec&dev_8168&rev_02 Instance Status Flags . . . . . : 0x180200a Device Manager Status Code . . : 0 IfType . . . . . . . . . . . . : 6 Physical Media Type . . . . . . : 14


EDIT for FUTURE SEARCHERS: Problem went away (on both computers) after I toggled the firewall setting in the cable modem/router interface (even though the original setting implied there was no restriction on icmp packets. It's not worded explicitly for that so I'm not sure.) The above diagnostic doesn't occur now either. Never did need to mess with ARP, or probably any of the other things I tried, including, probably, simple power cycling of the modem.