can't ping default gateway

i've a network with this ip range: -
I've 3 PC in this network can ping any other pc but can't ping the default gateway:
they can ping, access other PC share folder but default gateway, noway.
so could any help me to fix this problem.
i've shutdown all firewall on these 3PC.
and the problem is not with cable, because i replace that PC with my laptop and it can ping default gateway so well. but when i move failed PC to other worked pc to deal with workded pc cable, still can't ping.
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What hardware is your gateway?  If it is a router, PIX firewall or other appliance, it very well may have an option to disable responding to pings.  Check the settings on your gateway to affirm that it can respond to pings.
Is it only 1 PC that can't ping? Or all 3 can't ping but the notebook can?

If only 1 PC.. then try running this:
What is the Vendor name of your Gateway?
I think on Gateway ICMP packets are blocked. if you open its settings then there you can see the setting for allowing for ping.
Regards, ASIF
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Try changing your network to be in a range reserved for private use.

Any in through should be fine.
JunsieAuthor Commented:
i think there is something strange,because when i change default gateway to even ip address of 1 PC, it's can't ping even it own ip address.
Are you able to access the Internet (or any other computer) through the default gateway?  If you can, then the problem is definitely a setting on the gateway machine itself - look for ICMP enable/disable - that's the technical term for the packets sent/received by ping.  

Along with what frankenw is saying...  188.x.x.x is actually owned by a company in Amsterdam... so your computer (depending on the DNS settings, which if external is probably the case) is trying to ping a computer in Amsterdam rather than your gateway because they both have the same IP address.

I'd definitely recommend changing the IP addresses of your network to 192.168.x.x  (or even 10.0.x.x) with the correct subnet mask (since you only have a few machines, will do).  This will fix your problem (assuming your gateway is set to allow pings).
JunsieAuthor Commented:
i don't think so, because all other can connect to internet, while 3 pc is not, and they can't ping even there IP add address when its set as default gateway on ip configuration option. and other things is 3 pc can ping all other pc on lan network.
you could do a tracert to be sure

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JunsieAuthor Commented:
thanks,i've found out why this happen.
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