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I have a following issue

On my desktop computer I can't access internet. Precisely, i can't ping router. However I can ping other machines on local network and i'm getting IP from DHCP located on the same router.

In router log messages I found "Saturday November 21, 2009 14:10:07 Block MY_MAC-AB-A3-5E because no D flag"

I failed to find anything interesting in google.

Any ideas? (How make desktop add D flag to packets or stop router blocking traffic)

Desktop is running on Windows XP arp -a says that machine doesn't now MAC of router, however setting it to be static doesn't help either. Router is D-Link DI-524 I used to have internet on that machine, it stooped working recently, however i can't thing of anything that could cause that.

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That is freaky... have you tried contacting D-Link support? – MikeyB Dec 3 '09 at 14:27
up vote 1 down vote accepted

The TCP/IP Protocol Suite by Behrouz A. Forouzan says:

The D flag indicates that routing information for this destination has been added to the host routing table by a redirection message from ICMP.

Thanks Google for that...

So if a host learns of a route by receiving an ICMP redirect response it will add a dynamic entry to its routing table...

What does

netstat -rn

show on your XP machine please?

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I've added answer with result of netstat -rn – Grzegorz Dziemidowicz Dec 3 '09 at 15:02
Ok, so no weird routing set up which is good. Dos the Dl-524 support MAC filtering? Could it have just blocked your MAC address for some reason? I guess you would need another device (wired or wireless) to test this theory though. – Ben Z-B Dec 3 '09 at 15:45
+1 for answering my question :-P – Kyle Brandt Dec 3 '09 at 16:14
I found that indeed MAC was blocked. I need to find drivers (as i've uninstalled them :P) to confirm, but i believe it will fix the issue) – Grzegorz Dziemidowicz Dec 3 '09 at 17:34

What is the D flag? The DF (Don't Fragment Flag). If that is the case for Windows XP ping just use the -f flag to set that.

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just tried that, doesn't help (ping can't time limit exceeded, router logs blocking message) – Grzegorz Dziemidowicz Dec 3 '09 at 14:38
"ping time limit exceeded" – Grzegorz Dziemidowicz Dec 3 '09 at 14:38

netstat -rn

Tabela tras

Lista interfejsów 0x1 ........................... MS TCP Loopback interface

0x2 ...00 18 f3 ab a3 5e ...... NVIDIA nForce Networking Controller

=========================================================================== Aktywne trasy: Miejsce docelowe w sieci Maska sieci Brama Interfejs Metr       20       1       30       20 20 20       20 1

Domyślna brama:

Trasy trwałe: Brak

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Please try to empty your ARP cache by running this in cmd.exe: "arp -d *"

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