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Old October 11th 18, 04:37 PM posted to alt.comp.hardware.pc-homebuilt
Char Jackson
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Posts: 213
Default Mysterious internet/ethernet issue (kinda need testing/connection/communication service to diagnose it ???)

On Thu, 11 Oct 2018 01:24:50 -0400, Paul wrote:

wrote:
This is a bit of a long shot, but maybe somebody has seen something like this, I am thinking not but ya never know.

Situation is really weird:

My PC can play World of Warships fine, Company of Heroes via Game Ranger fine.

It can browse/websurf the internet fine.

It can even connect to another laptop over same ethernet port by pulling out internet cable modem cable and reconnecting to laptop etc.

But for whatever reason:

If computers from the outside try to connect to my PC it's not working.

Vice versa it's also not working ?!? Maybe cause those devices are natted.

But as far as I know my PC is not NATTED.

Or it's some strange/new ISP kind of NAT that behaves oddly.

Like only big companies/servers are still reachable and not consumer PCs.

As far as I can tell my PC does have a public IP address.

But apperently this is not working/enough anymore ?! Very strange.

I plan on replacing my PC with a laptop, just as a test, to see if it's the PC at fault and it's software, or if something more strange is going on ?!

What kind of electrical defect/or wear and tear could produce such a weird result ?!

(One thing which is on my mind is something different, a hacked or misconfigured/corrupted modem, which somehow blocks this).

For now I will keep assuming that everything is just fine on my PC and that it's the outside world that simply can't connect to my PC.

Though even laptop PC sometimes behaves weird as far as I can recall, but usually I can get it to work (?!) though now I am not so sure anymore.

It's not stupid firewall cause this is turned off and would usually allow anyway... it's something more strange.

I will try to get to the bottom of it though.

Also is there any service out there on the internet where there is a public computer that can send some traffic to a specific tcp or udp port ?!

Just to see if my PC can actually receive this ?!

That would be very helpfull.

Bonus would be if I can then send something back to it's udp or tcp port to see if that computer can also receive from me... and finally it reports this via a website/html or so... or even e-mail or so.

Bye,
Skybuck.


OK, so you did this.

ISP ------ modem/router ------- single_computer

Or, you did this.

ISP ------ modem ------- single_computer

In the latter case, Windows terminates the PPPOE protocol
coming from the modem. There's no NAT in that case.


PPPOE is a DSL-only thing and the OP didn't clearly indicate that he's
using DSL. Also, the presence of PPPOE, by itself, shouldn't be a
definitive answer to whether NAT is involved. PPPOE is just a tunnel for
getting traffic from point A to point B within the ISP infrastructure.
Its presence, or absence, doesn't tell us anything about NAT.

snip

Note that the router likely has "scanning detection"
and it can tell when one of these tests is running.


Some routers have that feature, but cable modems do not, and to my
knowledge DSL modems also do not, so it's important to get a clear
picture of the OPs networking equipment.

I used to have logging enabled on one of my routers,
and if I did a GRC scan, the log would have an entry
that the router had "closed the front door". This
invalidates the GRC test results, when the router
clams up for a few minutes and refuses to respond.
It gives a false sense of Stealth. So if you're using
a router with SMTP logging, check the log and make


That sentence should read, "So if you're using a router with
logging...". (Remove SMTP) With very few exceptions, networking devices
that can generate logs will default to storing those logs directly on
the device that created them.

sure the router doesn't notice what you're doing to it :-)
I can have my router send a log packet to this
PC, so I can see what's going on.


You're describing SNMP, but SNMP and SMTP (email) are just two methods
by which a networking device can send its logs to an external device.